Traitorfish
The Tighnahulish Kid
Humour is often explained as a response to incongruity, which I think has something to do with it. Conservatives are most often committed to the assumption that the world is fundamentally well-ordered and just, that whatever problems arise are because of specific individuals or groups behaving improperly, so they will less readily recognise the absurdities, contradictions or injustices which are the source of so much humour. The humourist is always fundamentally an outsider, and while people on the left are usually able to assume the viewpoint of the outside at least temporarily, conservatives who identify very strongly with inside-status find that much harder to do. Those conservatives who do have a well developed sense of humour tend to be the ones who are more deeply dissatisfied with the modern world, who don't buy so automatically into the idea that the status quo is worth defending, and so can occupy in at least some small way the position of an outsider.Also, apropos of nothing at all, conservatives really seem to lack a sense of humor. Like, they don't even see humor, much less generate humor.
I mean, there's also something peculiar about the sheer humourlessness of the American conservative movement, which I think has a lot to do with the widespread and deeply-rooted anti-intellectualism of the American right and the resulting suspicion of anything subtle or ironic. But as a more general explanation, I think the difficulty recognising or acknowledging incongruity is a lot of it.