Nobody would believe you if you just outrightly tell them you're a rapist like that. It is however expected that nobody would say it because people believe it would reflect badly upon them. This belief that it would reflect badly upon them is what makes it work, you say something that clearly shows you don't care what people around you think and are cool with making a joke about yourself in that way.

Basically you just showed that you were fun, able to have a laugh at your own expense, self validating and confident.

That's how you get away with that. In short - it's as you said Phil - being audacious.