To those who would, and do, mock the idea of political correctness: why have you even raised the subject?
I hadn't mentioned being PC, but I notice that those who have can be seen to use the term regularly, to the brink of obsession, and always disparagingly.
I also notice that nobody has offered an answer to the underlying question, viz:
What is it that amuses you about making a joke at the expense of an identifiable group of people (whoever that group might be)?
If you feel challenged by the question, then it suggests that you're not very secure in your belief. If you feel comforted by the growing number of people who seem eager to poke fun at me for asking the question, then it suggests that you're really just a bit of a coward. If you don't have any respect for the question, which was a serious one, and one that was put politely, then it suggests that you don't have very much respect for yourself.