There's no disagreement going on - unlike in the more famous examples of Linus Torvalds ripping into a person who he disagrees with (usually rightfully, and on solid technical grounds). And yet, pay attention to Dave Airlie's emails. From my past involvement in Mesa3D for the Radeon drivers, I know Dave a little bit, as a kind and friendly person. After the mail of Linus Torvalds, his tone changes significantly, using "crap" twice in a very gratuitous way.
The situation here isn't hostile at all, and yet the language becomes hostile after the supreme alpha geek enters the ring and the others begin to ape his style.
Of course, Linus Torvalds regularly defends this style by saying that it ensures that his message really gets through instead of being dampened by layers of friendly fluff, which he considers to be noise that distracts from the signal. There's truth in that. And yet, here we have evidence that the tone of discussion becomes unwelcoming even when all of the participants are on the same page. This is bound to create an unnecessary rise in serotonin levels at least in some people, which is bound to cause losses to the project.
So is this style really necessary to successfully run a large scale open source project? The answer appears to be No, given how many other projects exist, and how few of them create the kind of noise about their internal conduct as the Linux kernel does.
I do find it interesting to observe that there is possibly no other person in a comparable situation to Linus Torvalds, simply by virtue of how the development of the Linux kernel is structured. Even though he has delegated most of the work, all changes to the Linux kernel eventually must pass through him, as he is the only person who can change the project's
masterbranch. Compare this to other large open source projects, all of which (to my knowledge) allow their master branch to be written to by a group of core developers. It seems to me that there is a curious feedback loop going on between Linus Torvalds' character and the environment he operates in.