Have you actually read some of his messages? He is mostly very nice and patient with new people but he can be harsh with experienced people who should know better in his opinion. He also almost always attacks the idea, not the person and explains his rationale. I'll take someone like him any time over a lot of corporate people who regularly go through their politeness rituals without ever making progress.

And I think the history of Linux proves him right. It's phenomenal that he has been able to keep it together and thriving for so long. That's a pretty rare achievement.

Mostly very nice is irrelevant. Being an asshole a tiny fraction of the time is still unnecessary and counterproductive.