For the most part he is extremely knowledgeable within his field and has a pragmatic outlook that I like a lot.
At the same time, anyone who presents incredibly complicated topics as black and white rarely has their facts straight. That by itself is a huge red flag. They're either misinformed at best or lying to you at worst.
In Linus' case, I usually give him the benefit of the doubt and assume that his stated black-and-white opinion is a vastly simplified version of his much more nuanced and informed opinion that he keeps to himself. Sometimes he makes me think I'm giving him too much credit though. Abrasiveness always makes me question someone's credibility when used in defense of a binary opinion on a complicated topic (this applies to anyone, not just Linus).
The funny thing is that here on HN, Jobs generally gets a nod for behaving like a bastard ("because that's what's needed to make a good product"), but Torvalds gets demonised. Even de Raadt, famed for his abrasiveness, is accorded respect for it. It puzzles me on two fronts, because Torvalds really isn't that abrasive unless you really push him, and that for some reason, he doesn't get respect that other tech 'names' do for (supposedly) being so.
If you can laugh at yourself, it is less abrasive than it seems. If you can't it's infuriating.