The answer is that parts of the left have little or no belief in the concept of "decency" as traditionally understood by Western civilization. They tend to dismiss such notions as bourgeois anachronisms; they place great value on individuals expressing themselves; and they view self-censorship as a form of fascism.

This latter reason is important: The '60s redefined narcissism as idealism. The individual's feelings became sacrosanct.

That is why the self-esteem movement -- the idea that how an individual feels about himself is far more important than what he actually accomplishes -- arose from the left.

And that is why you almost never hear a conservative say "I am offended" when reacting to a liberal speaker or writer, but it is quite commonplace for a liberal to use those words in reacting to someone from the right.

"Make love not war" was another example of placing one's feelings above other values. That is why it is a very good thing for the world that the previous generation, the one that fought Hitler, didn't believe in making love rather than war.

For more than a few people on the cultural left, public cursing is simply a form of self-expression, just as many on the left deemed graffiti to be. Indeed, public cursing may be defined as verbal graffiti, a defacement of the public square. But the people who believe in the sanctity of the public square are far more likely to be on the right. And that is why you will see and hear far more public profanity on the left than on the right.