I don't know. By swearing, it tells me that he spends more time caring about their feelings. If he could just say "No" instead of "Fuck no! I'm not accept that shit!" he'd save a lot of time and energy dealing with people's feelings.
If he said "no" instead of "fuck no!" he wouldn't have gotten the message of how fucked up the code is across.
Yet, incredibly, I don't have to use the word "fuck" at all. Amazing, I know. It's as if it's possible for someone to listen to criticism and improve their work without having to be screamed at. I have funny memories in which this happened to me as well; I wrote bad code, and then someone explained to me what was wrong with it, and then I wrote better code. Again, nobody said "fuck". Truly amazing.
For some yes. Doesn't work with all.
So, what is it really solving? Nothing for new contributors. Nothing for old contributors.