In a ProJo story about the annual reading of George Washington’s Letter to the Touro Synagogue in Newport, Brown University President Ruth Simmons is quoted thusly:

She touched upon the moral contradictions underlying the noble desires of past leaders who were eager to uphold freedom, despite an indifference to the injustice of slavery.
“We all know that these lofty and compelling ideals were largely omitted from discourse when it came to Africans and Native Americans.… In failing to apprehend the corrosive evil of slavery and the immoral inequities that it was to create for generations of descendants, Washington compromised his legacy as a moral leader,” she said.

This is simplistic. Historians agree that Washington’s views on slavery certainly evolved from his early manhood up until he freed many of his slaves in his last will. For Simmons to opine that he “fail[ed] to apprehend the corrosive evil of slavery and the immoral inequities that it was to create for generations of descendants” betrays a blindered view of history. The fact is, Washington was hardly indifferent and fully recognized the evils of slavery.

In a letter to the Marquis de Lafayette on May 10, 1786, Washington wrote:

The benevolence of your heart my Dr. Marqs. is so conspicuous upon all occasions, that I never wonder at any fresh proofs of it; but your late purchase of an estate in the colony of Cayenne, with a view of emancipating the slaves on it, is a generous and noble proof of your humanity. Would to God a like spirit would diffuse itself generally into the minds of the people of this country; but I despair of seeing it. Some petitions were presented to the Assembly, at its last Session, for the abolition of slavery, but they could scarcely obtain a reading. To set them afloat at once would, I really believe, be productive of much inconvenience and mischief; but by degrees it certainly might, and assuredly ought to be effected; and that too by Legislative authority.

In September of that year, he wrote to John Mercer:

I never mean (unless some particular circumstance should compel me to it) to possess another slave by purchase; it being among my first wishes to see some plan adopted, by which slavery in this country may be abolished by slow, sure, and imperceptible degrees.

He wrote to Charles Pinckney on March 17, 1792:

I must say that I lament the decision of your legislature upon the question of importing Slaves after March 1793. I was in hopes that motives of policy, as well as other good reasons supported by the direful effects of Slavery which at this moment are presented, would have operated to produce a total prohibition of the importation of Slaves whenever the question came to be agitated in any State that might be interested in the measure.

Or Lawrence Lewis, in August of 1797, that:

I wish from my soul that the Legislature of this State could see the policy of a gradual Abolition of Slavery…

Yet, amidst this, he very clearly did equivocate with regards to his own slaves. For instance, in his letter to Tobias Lear on April 12, 1791, concerning the anti-slavery laws in Pennsylvania: Philadelphia, as the capital then, would be Washington’s home and he was concerned with how to maintain his own slaves without having them freed (As they would be if in Pennsylvania for over 6 months). And he went to secretive ends to assure his hold on them:

…in case it shall be found that any of my Slaves may, or any for them shall attempt their freedom at the expiration of six months, it is my wish and desire that you would send the whole, or such part of them as Mrs. Washington may not chuse to keep, home, for although I do not think they would be benefitted by the change, yet the idea of freedom might be too great a temptation for them to resist. At any rate it might, if they conceived they had a right to it, make them insolent in a State of Slavery. As all except Hercules and Paris are dower negroes, it behoves me to prevent the emancipation of them, otherwise I shall not only loose the use of them, but may have them to pay for. If upon taking good advise it is found expedient to send them back to Virginia, I wish to have it accomplished under pretext that may deceive both them and the Public; and none I think would so effectually do this, as Mrs. Washington coming to Virginia next month (towards the middle or latter end of it, as she seemed to have a wish to do) if she can accomplish it by any convenient and agreeable means, with the assistance of the Stage Horses &c. This would naturally bring her maid and Austin, and Hercules under the idea of coming home to Cook whilst we remained there might be sent on in the Stage. Whether there is occasion for this or not according to the result of your enquiries, or issue the thing as it may, I request that these Sentiments and this advise may be known to none but yourself and Mrs. Washington . From the following expression in your letter “that those who were of age might follow the example of his (the Attorney’s people) after a residence of six months”, it would seem that none could apply before the end of May, and that the non age of Christopher, Richmond and Oney is a bar to them.

Clearly, Washington wasn’t above subverting his ideals the closer the issue of slavery got to home. However, he also recognized the evils of slavery even if his actions failed to align with this recognition. One common defense of Washington’s actions is encapsulated at the MountVernon.org website:

Washington did not lead a public fight against slavery, however, because he believed it would tear the new nation apart. Abolition had many opponents, especially in the South. Washington seems to have feared that if he took such a public stand, the southern states would withdraw from the Union (something they would do seventy years later, leading to the Civil War). He had worked too hard to build the country to risk tearing it apart.

Historian Dorothy Twohig elaborates:

For Washington, as for most of the other founders, when the fate of the new republic was balanced against his own essentially conservative opposition to slavery, there was really no contest. And there was a widely held, if convenient, feeling among many opponents of slavery that if left alone, the institution would wither by itself. Ironically, the clause of the Constitution barring the importation of slaves after 1808 fostered this salve to the antislavery conscience by imparting the feeling that at least some progress had been made.

Further, Twohig explains that Washington, essentially an aristocrat, was nervous about the emotionalism of many abolitionists (particularly Quakers). To that end, she observes:

…given his accurate conception of his own great and pivotal role in the infant country and his fears for the survival of the Republic itself, it is far from likely that he was ever sorely tempted to open as a national issue the Pandora’s box that the Constitutional Convention appeared to contemporaries to have closed for the next twenty years.

It is a tragedy that neither he nor the other Founders took action sooner, but their primary concern was with safeguarding a nascent nation, even if that meant sacrificing the central American ideals of freedom and liberty in the process.
However, it is last will and testament that probably indicates his final, and true, feelings on the matter of slavery.

Washington once told a visiting Englishman that slavery was neither a crime nor an absurdity, noting that the U.S. government did not assure liberty to madmen. “Until the mind of the slave has been educated to understand freedom, the gift of freedom would only assure its abuse,” Washington explained.
His will, drafted a year later, said otherwise. He wrote that he wished he could free all the slaves at Mt. Vernon, but couldn’t because some belonged to his wife’s heirs, and he didn’t want to divide families. Unless Martha or her heirs freed the Custis slaves as well, families would be broken up. [Henry] Wiencek [author of The Hairstons: An American Family in Black and White] believes George was trying to persuade Martha to use her influence on her heirs to free the Custis slaves–but she did not. Washington also stipulated that the freed children be taught reading, writing and a trade.
“His will was a rebuke to his family, to his class, and to the country. He was well ahead of people of his time and place,” Wiencek said. “This is George Washington’s true legacy. He’d said the slaves weren’t ready for freedom, but at last he said they must have it because of their humanity.”

Yet, as historian Dennis Pogue comments:

Washington’s will swiftly gained the public attention envisioned by its author, appearing in print almost immediately, with no less than 13 editions published in 10 different cities in 1800 alone. And yet, if Washington hoped that the decision to free his slaves would compel large numbers of his countrymen to follow his lead, he was sadly mistaken.

His final act, though noble, didn’t inspire the sort of change that he foresaw. He tried–if only fitfully and sometimes half-heartedly–to end slavery. He could have done more. Yet, Simmons’ critique that Washington “fail[ed] to apprehend the corrosive evil of slavery” is clearly wrong. He knew it was immoral and that its existence ran counter to the claims of the American Revolution, but he felt his hands were tied by the practical politics of the day. Further, it is unfair of Simmons to expect that Washington could have had the Delphic vision to see “the immoral inequities that [slavery] was to create for generations of descendants.” Like the other Founders, Washington believed that slavery would wither away. He was clearly wrong. Nonetheless, he recognized that to succeed, slaves (or former slaves) needed to be educated and prepared for a life of freedom before actually being set free.
Ultimately, Washington’s failure was one that became more obvious as time went on. He and the other Founders kept the nascent Republic together by acceding to the political practicalities of the day. This meant acquiescing temporarily–as they truly believed–over the issue of slavery. Retrospectively, it is indeed a failure to uphold the American ideals of freedom and liberty for all.
Perhaps Simmons was trying to say that the failure to deal properly with the slavery issue shows that Washington and the other Founders weren’t really as great as we should have hoped. Such an argument is hardly new, especially in academic circles. But Simmons has taken a now-common recognition of the acute failure of the Founders with regards to slavery–a critique that is deserved, if in context–and applied a layer of hyperbole that that results in skewing the perspective too much the other way. It is both undeserved and innaccurate. Washington’s writings indicate he was at times rueful, at times hypocritical, and at times idealistic about the issue of slavery and its eventual end. Such conflicting thoughts and actions made him all the more human and make it all the more remarkable that he was able to do what he did.