I think you're conflating two different things. Yes, Linus is very strict about not breaking userspace. But the swearing doesn't come from some void somewhere:

I think you're conflating two different things. Yes, Linus is very strict about not breaking userspace. But the swearing doesn't come from some void somewhere: it is directly aimed at enforcing the rules of not breaking userspace. If Linus didn't occasionally get angry about it the people below wouldn't take it as seriously, and the kernel wouldn't as stable a target.