I think that a lot of so-called denigrating humor is using a specific strategy. Post-irony is not easy to wrap one’s conscious mind around. By specifically demonstrating the subtle, underlying biases in cultural norms, the idiotic clinging to stereotypes and other forms of prejudice, even the way we react to overt shock value demonstrates that subconsciously, prejudice and bias are abhorrent to our humanity.
Now, one has to tread these waters lightly, because not used properly post-irony can appear as actual hatred, prejudice, and plain meanness. Professional comedians use this strategy a lot, including the much loved Stephen Colbert. Also think about Dave Chapelle. A lot of these strategies started in camp culture, imo.
Having said that, some people are just crass and inane. But I have to admit, I laugh, if I’m not offended. But I never laugh at people. That’s not true, I’ll laugh at the truly ridiculous, but doesn’t everyone?