Wow, I’d never heard that theory before!

Socrates being entirely made up by Plato is less of a theory and more of a joke, this is a meme community after all. The part of Plato being a boxer, and using this fact to reinforce his arguments, however is true.

Soo was Diogenes a good fighter too? I feel like the thing with the plucked chicken would have been provocative even if the speaker isn’t prone to violence.

No idea, but it is well known that he was very good at doing things like wanking in the middle of market square in broad daylight.

I'm sure there was a reason or another for people not getting violent for all the things he did. If I had to guess, from the fact of him living in an old barrel, I'd infer that nobody wanted to touch him due to his surely poor personal hygiene.