Reddit recently had a question posted asking their community to submit the most offensive joke(s) they knew.
There's some pretty disturbing material here and if you doubt the power of the written word to affect people just as much as the visuals of pornography or the sound of foul language, look no further than this thread. It's sort of like a bunch of mini-me versions of the Aristocrats joke.
I was looking for a tamer joke to copy here as an example but I honestly couldn't find one. (That should be sufficient warning for anyone debating whether to click through to Reddit or not – or perhaps incentive for some!)