Jonah Goldberg posted a letter in the Corner that’s worth reading in its entirety, but here’s the crux:

To be blunt, in the days of my grandfather, a good sized group of men would have peeled off from the funeral, and informed Rev. Phelps he was not welcome within eyesight of the funeral, and that it was time for him to leave. Like, right now. If he didn’t, then he would have been bodily removed, likely with a variety of lumps and bruises, from the scene and warned that if he returned, he would get a serious beating.
And nobody would have batted an eye. Any cops that were called would have exercised discretion, looked over the situation, and told Phelps “You had it coming, bub, beat it”. Any judge that Phelps petitioned would have looked at the case, told Phelps he was a horses hind end, and tossed it out of court with prejudice.

The writer goes on to suggest that the difference was a uniform culture, at least with regard to standards of behavior. In essence, everybody in the entire chain of events would have understood that the judgment from the jurist’s bench would have found any assault charges mitigated by Phelps’s offensive action. Now things aren’t so clear.
One needn’t believe that judges ought to apply their own cultural bias to every situation to come their way to think that some reasonable degree of self policing ought to be understood as undeserving of courts’ time and attention. The letter writer above blames the left’s post ’50s “smashing [of] cultural norms, [which] moved simple disputes such as this from the cultural, low-level form of conflict resolution into the legal system.” Somebody more sympathetic to ’60s radicalism might adjust that statement to note that the disruptive decade allowed actually existing subcultures to make their presence known, thereby necessitating recourse to the ostensibly neutral intermediary of the law.
Both of these factors surely play a role, but I’d suggest that the larger problem is the division of the culture between elite and masses, high and low, ruling and ruled. The richest man in town once sat among the pews with the common folk, presumably admitting the authority of a shared church. Less mobility meant that powerful people were often in closer proximity to the hoi polloi, making them more accessible. The absence of all sorts of technologies — from instant communication, to rapid transportation, to forensics and other investigative techniques — meant that leaders who presumed too much in the face of popular will were vulnerable to street justice, themselves.
That isn’t to say that street justice is desirable, but all of these factors together once fostered a cultural sympathy and a sense of extra-legal accountability, creating incentive for everybody to remain within a tolerable variation from cultural expectations. And as the Phelpses’ offensive roadshow illustrates, our society failed to maintain important cultural controls as it made desirable adjustments to allow greater individual freedom and a stronger voice for those outside of the mainstream.
That, in my view, speaks to the real damage done by the radicals of recent decades and progressives of the past two centuries: They’ve pushed for rapid change, typically leveraging emotion and legal imposition to simply make a new social structures fact without regard to the pillars that might fall as a consequence.