That is true, but Linus was still being an ass, and unfortunately, seems to be doing his utmost to establish a reputation as a geek bully who uses his success as a club to beat up enthusiastic volunteers. He should know better. And this is not the first time, far from it.
I don't think Linus was being an ass here. From what I could see, this email was just the last in a fairly long discussion where someone introduced an unexpected behaviour that manifested itself in a whole lot of places as a bug. Mauro then claimed it was the userspace apps' fault. After debating for a while, Linus blew his top and told the guy to stop making excuses.
I can certainly relate to that.
I wonder, though, what's the procedure for introducing incompatible changes that will break userland, e.g. if there is some design error that causes a security flaw...