I don't know about every project and they all have different possible issues. I imagine given what we've heard about Linux and Linus himself, it has to do with the long standing culture of open source to be tolerant of behavior that wouldn't be acceptable in the workplace.
Linus can call someone a fuckwad or say their code is shitty, that its not a dick sucking contest etc... on an email list, but admittedly if he had done this in most first world conference rooms he would have been taken down to HR for being an ass. The "other side" is basically saying because of this kind of behavior, it makes people who are not already okay with that kind of behavior, not want to contribute. If Linus had said "This code isn't anywhere near the level of proficiency necessary to merge much less directly into the kernel. Work on your skills, submit to other projects and modules etc... but you're wasting your time and mine by bringing this across my desk. Please adhere to our policies and do not bring this in here again", instead of "FUCKING KILL YOURSELF THIS IS SHIT", they wouldn't be able to bitch.
I guess in theory a CoC, if a line of it basically says "You can't curse at people, call them names, or insult them personally as opposed to their work", it means everyone knows that and attempts to adhere to a single standard of behavior in that regard? The same way you can't fling shit at coworkers who annoy you.
