Some comments from Michael, of Rescuing Providence, touch on basic differences of assumptions and perspectives. The first was to my “Proud to Be Non-Union” post:

I never expected the folks here at Anchor Rising to be pro-union, but the depth of misunderstanding concerning organized labor and the willingness to serve as lackeys to powerful corporate thugs is unbelievable. When will people realize that most of us will never be rich! Our system, once fair and healthy now works against the individual. We are not the “investor class.” Without organized labor we’ll be no better off than the slaves in China. Unions are not the enemy.

Perhaps I’ve a tin ear for this tune, but it sounds as if Michael is expressing doubts that individuals can at the same time be autonomous and substantial. To wit, the only counter to powerful corporations is powerful union organizations (with or without their influence on powerful government). The only way to avoid servitude is to submit to collective management.
My own perspective, as one of those unaffiliated slavish lackeys, is that I have sufficient personal value to my employer to negotiate fair terms; if we cannot agree, then either I am not achieving what I ought or he is not conducting business as he ought. Whichever proves true, artificially perpetuating the relationship would maintain a state of affairs that ought to change. Worse, forcing my employer to give me more than he believes I’m worth will not make him a better businessman; it will lead him to move the burden of his bad practices elsewhere (and with the benefit of my talents).
A company may seek to exploit those workers who are not individually indispensable, but it will seek to capitalize on — and retain — the talents of those employees who make themselves valuable in their own right. But through the dictation of employment terms, a union draws a line between those who are within its fold and those who are not. Unionists present the latter group as too-wealthy executives (or greedy, nepotistic politicians), but the pain of their smaller pie is more likely to be felt by lower-tier professionals and those who are not employed at all (a group that can include former members of the union). In The Road to Serfdom, F.A. Hayek suggested that Nazism was “a sort of middle-class socialism… to a large extent a revolt of a new underprivileged class against the labor aristocracy which the industrial labor movement had created.” I couldn’t help but think of Rhode Island’s current situation when I first read Hayek’s next paragraph:

There can be little doubt that no single economic factor has contributed more to help these movements [i.e., fascism and National Socialism] than the envy of the unsuccessful professional man, the university-trained engineer or lawyer, and of the “white-collared proletariat” in general, of the engine driver or compositor and other members of the strongest trade-unions whose income was many times theirs.

Contrary to Michael’s protestations, to those whose lives are adversely affected by being outside of the union’s embrace, the union is the enemy. And to the extent that we accept his view of employers as the enemy, those folks are only the more without friend. The only way to ensure that nobody is harmed by outsiderdom would be to force everybody into the same group; in other words, to bring about communism. Unfortunately, if our initial premise is that the individual cannot combat the will of those who are more powerful, it makes little sense to consolidate power totally. Those wealthy thugs will find themselves in the best position to transition into powerful positions in a system that will now allow them even more liberty in controlling circumstances to their advantage.
This ties into the reason that Michael is right about communism, but that it is in all of our interests to prove him wrong about capitalism:

Communism in its purest form might actually work, however, nothing is pure and communism was doomed before it got started, thankfully taken down by human nature. Human nature, in my opinion anyway, is what will be the downfall of capitalism. Too few have too much, whether earned or inherited. The system as we know it is destined for collapse, maybe in our lifetime.

The relevant quality in human nature is the inclination to seek improvement of one’s own situation. Communism restricts the majority’s ability to do so significantly, while increasing the planners’ ability. Capitalism, by contrast, is designed to thrive on individual autonomy, so the same quality in human nature asserts itself as restrictions placed on others, increasingly by means of restricting everybody such that those whose advantages place them beyond an initial barrier have freer rein. Regulations — and unions — ensure that the truly powerful are less likely to find themselves threatened by competition, and the remedy is to enable that competition.
I’d note that the complaint of human nature applies backwards in the logical progression to unions, and is visible in another of Michael’s comments to the first-linked post:

I have no desire to defend public or private unions. I only speak of my own experience. My union leaders are not thick necked thugs. Local 799’s president is a front-line highly decorated and respected firefighter and an attorney, our vice-president is a fellow Bishop Hendricken grad, class of ’80 and a class act, our secretary treasurer is one of my best friends, a great firefighter and better rescue lieutenant and a CPA. The image of unions as a bunch of thugs who care nothing about anything but themselves is plain wrong.

No doubt all of Michael’s friends and fellow union members are good guys; I’ve no desire to treat them as Michael treated corporate executives when he lumped them together and called them “thugs.” But note their close-knit nature, as Michael frames it. Note also the other attributes by which he describes them: an attorney, a private-school graduate, and an accountant. These are people who may indeed turn out to be rich, and who are certainly not a misnegotiation or two from slavery. I humbly suggest that there’s a disconnect between the union rhetoric and its apparent reality.
Be all of this as it may, I’m among those who believe that firefighters and rescue workers ought to be well compensated for their work, which means that I agree with most of what Michael writes in a final comment:

I could go into detail about the lives I have saved (there are many) and property I have protected but I would rather not. The reason I do what I do and risk my health and my family’s welfare is because my union negotiates benefits that our elected officials would take away in a heartbeat to fund somebody’s friend’s project, create a job for somebody’s cousin or simply line their pockets. As taxpayers we should want the best equipped, staffed and trained personnel available. Instead, the sentiment in business, more for less, has pervaded our public safety agencies. Don’t think for a second that thousands would line up for my job if I quit tomorrow and there was no reward. My job is hard, as I’m sure yours is. I’m not wealthy but I make a good living and have my union to thank. That my living is funded by taxpayer dollars does not make me less worthy. I have no intention of quitting unless things get so bad I can no longer afford to be a firefighter. If that happens, I’ll get by, I always have. I made a lot more money before I became a firefighter.

As taxpayers, we should want the best equipped, staffed, and trained personnel available, which is why I’m not sure that unions are necessary to give them a boost. Under a healthy system, were elected officials to abuse their power at the expense of the security and safety of their constituents, somebody or, in a worst-case scenario, some tragedy would expose their behavior, leaving them open to electoral or even criminal repercussions. Paying critical personnel well below their worth would not be long sustainable.
As we see in Rhode Island, however, the clout of special interests, including unions, keeps our system from being a healthy one. The evidence that leads Michael to speak of the “heartbeat” speed of corruption is, in part, made so — and made to be accepted by way too many Rhode Islanders — by the interplay of powerful forces in the state. If everybody forms activist groups in their own interests, there remains only a battle between groups, all with some degree of sympathy for the corrupt behavior of the others. This is not to say that Michael or any of his coworkers condone or engage in corrupt behavior, but although there is a spectrum along which to balance principle and the insider-mentality, human nature will tend to present a group’s benefit to one’s self as deserved, but the benefits to others from their competing groups as suspect.