If the joke is just being rude for the sake of shocking the audience, then yes, that's cheap humor. What about satire though. There's some classic comedy that was 'offensive' to people who had no idea what the joke was.

For instance the Brasseye pedophilia special is some of the funniest, cleverest TV ever.

http://en.wikipedia.org/wiki/Brasseye#2001_paedophilia_speci...

Politicians described the show as "unspeakably sick" (while admitting that they had not seen the programme).