I would argue that conservatism is inherently anachronistic and rife with contradiction. It's not funny to make fun of people for being less fortunate than you. Daniel Tosh can do it, but his comedy isn't political, and it's also very self-aware and turns inward as often as outward.
Rush Limbaugh's "jokes" take the form of "Equality is for white men," whereas John Stewart's take the form of "Equality is for white men, and that's fucked up." Protecting the status quo isn't inherently funny, because the status quo is what causes so much suffering.
Trey Parker takes stabs at liberals all the time. I would say probably more often than conservatives. But he does it in a way that isn't about making fun of the less fortunate, but rather by pointing out the hypocrisy in their ideology (because all ideology is hypocritical to some extent), and the self congratulation with which they often treat themselves.