Random people saying ****

So I'm walking downtown, coming from a bar, and a guy I swear I don't know walks up to me and says

" So anyways, to finish my story, There I was, an ankle in both hands, up to my nutsack in this guy's ass, but the joke's on him cause I'm not gay."

Why is it that people do things like this, and how do less well-mannered people than myself not assault those saying such crass things with no provocation?

Don't get me wrong I say crazy stuff around those I know, but this really shocked me and presented me with an anomaly, something knew to understand. This guy wasn't visibly drunk and was walking with what appeared to be his wife and child. He was maybe 25.

Anyone else do things of this nature?

What is the psychological motivation?

Cambraceres