You can be polite or just straightforward and still get your message across.

"We don't blame bugs on user programs", "This is not an error code that should be used here", "Your coding standards may have relaxed over your tenure, be sure to maintain quality code.", etc. I get the annoyance, but you can be firm without yelling, especially in a professional environment.

Edit: Seeing the full context of Mauro's message (posted below), I can see why Linus took this tone. Mauro was being pretty condescending to a dev.