"It is impossible to be irreverent when the world no longer believes in reverence. It is impossible to tell an “edgy” joke when the edge has moved before you finish telling it. It is impossible push the envelope when there are no boundaries that envelop. Our entertainment and humor is degenerating fast because there is no stable context for it. In fact, today’s humor is often forced to establish a context – usually a caricature consisting of a “repressed”, conservative, religious milieu that most people have never experienced – for some protagonist to violate. Increasingly, however, Political Correctness has taken the place of Christianity, and some of the new comedians apply their irreverence to PC dogma, although it changes so fast it’s hard to keep up with, forcing the violators to anticipate the next move and push the envelope still further. An obvious problem with this is that PC is itself a caricature of its host, Christian morality, and it is not uncommon for the two to overlap in places. What offends against PC, often enough, offends even more egregiously against its predecessor."
More here, in this blog post from 2008.