Some people think that directness and honesty is identical to saying racist, sexist, and homophobic things. So "PC" becomes equivalent to "lying to make people like you."
Not any serious people, so why do we care?
From what I've gathered the findings are based on real data.
Citation? Sounds interesting.
I tend not to take my own mistakes very seriously unless they come with serious consequences. Having someone I respect tear into me would, I think, force me to take greater care and apply more attention to my work than I already do.
I've heard similar anecdotes from people who have contributed. I even recall a female contributor say something positive about it.
If anything you'd have trouble getting code in because maintainer thinks it would add more complexity than is necessary, or would make his job harder in the future, or after writing and testing the code, you'd find out you should have been doing things differently, etc. These are much more probable ways to get discouraged from contributing kernel code.
There's a high bar to getting code in, and that can be frustrating. But it also keeps the mainline attractive to users and developers, because of ever improving code quality.
"What the fuck is this? This came from Satan's butt-hole. Kill whoever did this - kill them immediately, here, I'll go and find this asshole who submitted this patch, and do it for you, you lazy ingrates, why do I have to do everything around here?"