Why do people like to be offensive/racist/edgy? I mean psychology wise - what is the explanation for the behavior?

I have come up with a partial list:
1). To get a reaction
2). To feel superior
3). To amuse oneself

I think that for me it seems very disassociated from my mental state - I am normally never offensive in my head, actually kind of nice, but in my online writing I can be extremely offensive, and I have no clue why. I feel less it is about me - and more about how being polite is a game, and I am being tricked into not abiding by the rules, despite the fact that usually in most circumstances I would be following the rules of politeness automatically.