Since OSS projects are easy to create and it's easy for developers to move from project to project

Creating projects is easy; forking is hard. And nobody wants to create a new kernel from scratch. Kernel hackers don't really have a lot of options. So I don't think your theoretical world has anything to do with the real world. Also, it seems to me that culture doesn't end up contained within a single project; Linux depends on GCC, for instance, so the Linux people have to interact with the GCC people. Which means that culture will bleed over. I was recently at a technical conference and a guy there said, "yeah, security is perhaps the only community that's less friendly than Linux kernel development." So now it's not just one project that's off-limits, but a whole field.

I also don't think there are necessarily any actual roar-and-smash types. That is, I think a fair number of people think it's fun to lay a beatdown on some uppity schmuck. I've experienced that myself, certainly. Why else would anyone bother wasting time arguing with creationists? But I'm not sure there are a lot of people who find it fun to be on the losing end of this. This is an extension of Arguments as Soldiers. When you're having a knock-down, drag-out fight with someone, it's harder to back down.

Notice that the original example of a person in that category was Mannie O'Kelly -- a fictional character.

Put yourself into manager's shoes

[Linus]:

And I do it partly (mostly) because it's who I am, and partly because I honestly despise being subtle or "nice".

(later in that email, he does give a nod to effectiveness, but that doesn't seem to be his primary motivator).

I think it remains an open question whether Linus's style is in fact better than the alternative from the "get shit done" perspective. And the original quote implied, without evidence, that in fact it is. Not really sure why this is a "rationality" quote.