I'm probably in the minority here but I just don't think it's FUNNY to joke about people because they're 'different'.
Whether it's a 'different' colour, sexuality, mental or physical competence, religion .....
I think there are plenty of things to be laughed at. Difference and disability don't feature as far as I'm concerned. I'd find it hard to be comfortable with myself if I offended someone by joking at their 'difference'.