> I find more often than not, that "abrupt and to-the-point" is mistaken for "rude and offensive".

Calling someone's theory bullshit is rude and offensive. Telling someone they are full of shit is also. Abrupt and to the point as a general class of communication further is often rude. Making or attempting to make people feel worse than you need to to get your point across efficiently is offensive.

In this case, for example, Linus could have simply said, "That's a nice theory. If you can prove it, we'll consider it." That's more to-the-point, communicates the entirety of what Linus managed to in his email, and also is not rude.