In the Commentary essay (reprinted here) that inspired his new book, Camelot and the Cultural Revolution, James Piereson wrote:

There is much about Oswald and the assassination that can now never be known for certain. Of one thing, however, there can be little doubt: there would never have been any serious talk about a conspiracy if President Kennedy had been shot by a right-wing figure whose guilt was established by the same evidence as condemned Oswald. Such an event would have been readily understood in terms of then prevailing assumptions about the dangers from the Right. Kennedy’s assassin, however, bolted onto the historical stage in violation of a script that many people had assimilated as the truth about America. Instead of adjusting their thinking accordingly, they strove to account for the discordance by taking refuge in conspiracy theories.

As I've written before, this sort of paranoia was associated in the 1950s and early-60s with the fringe elements of the right, before the inability to process Oswald's ideology was one of the first key sign of a far left becoming increasingly batty.

Similarly, the overheated language of the modern left, such as Al Gore’s recent attempt to demonize his critics as “Digital Brownshirts” also begins to grow out of this mid-1960s period. “Just as the Birch Society had accused Eisenhower of being a communist”, Piereson recently told me in an interview, “by the late sixties, the liberals and leftists were accusing everyone else with being Nazis and fascists."

You can see both elements at play here:

The nation’s first Muslim congressman said Tuesday that he erred in comparing the Bush administration’s response to Sept. 11 to an event that led to Adolf Hitler’s consolidation of power in Nazi Germany.

At an appearance before a group of atheists in Minnesota on July 8, Rep. Keith Ellison, D-Minn., called Sept. 11 “the juggernaut” that led to war, tolerating torture and increased discrimination against religious minorities.

“It’s almost like the Reichstag fire, kind of reminds me of that,” he said. “After the Reichstag was burned, they blamed the Communists for it and it put the leader of that country in a position where he could basically have authority to do whatever he wanted.”

Ellison has since issued a sort of non-apology apology for his remarks; the whole thing is very much in line with the "blurt and retreat" strategy that Steven Hayward described recently in regards to an even more prominent member of the left.