For example, one of Jimmy Carr joke:
"My girlfriend told me that she can no longer continue our relationship because people said that i am a fking pedophile. I answered: 'Watch your mouth, that is some big word you are throwing out for a 10 years old'".
It's funny because we know that Jimmy Carr is an upright citizen and a comedian. Imagine a convicted pedophiles say the same lines, won't feel as funny isn't it?
Actually, given how many popular entertainers have been revealed as awful people (Bill Cosby, Bill Murray, Jian Ghomeshi, etc.) these days, that actually comes off as kinda creepy.