My guess: if Linus would behave in a nicer, politer way, the Linux kernel would be much more awesome than it already is. Through his behavior and that of the people he has attracted (those that will deal with his shit and have a higher incidence of behaving in the same way), hundreds of would-be contributors have been annoyed, alienated and scared away.

If you questioned every developer on this planet, for every kernel contributor, on every level of expertise, there are two that simply wouldn't deal with his shit and have been lost. The Linux kernel could have been much better.