Possibly because some people (myself included) would actually volunteer to work under someone like this--because "caring enough about the product to get angry" is actually a useful quality in a leader, if you believe in the product and want it to succeed (rather than just being there to make your pay and not make waves.)
Of course, if he also gets angry about not-the-product, he might be horrible to work with--but I've never seen this to be the case; Linus seems like a genuinely nice guy in every other situation.
I also quite like the bluntness in that it is very clear what his opinion is, I can easily understand where and how I went wrong and actively work to correct this.
Of course, if he also gets angry about not-the-product, he might be horrible to work with--but I've never seen this to be the case; Linus seems like a genuinely nice guy in every other situation.