From an interview in the October 2003 issue of Playboy magazine:
PLAYBOY: You started in stand-up. Which comics do you admire and which do you hate?
JOE ROGAN: The comics I hate are thieves. Nothing's more disgusting than a guy who steals another person's ideas and tries to claim them as his own. Stand-up comedy is supposed to be "Here's the world through my eyes." It's supposed to be your observations, your thoughts and views on life. When you snatch little pieces of other people's lives and try to palm them off as your own, that's more disgusting than anything. Robin Williams is a huge thief. Denis Leary is a huge thief. His whole stand-up career is based on Bill Hicks, a brilliant guy who died years ago.
[Leary responded, Joe Who?]
sad