Or maybe he's just so talented that he can carry a huge interpersonal handicap.
Actually, this email is pretty polite and to-the-point. I don't know exactly what it is that he said that was offensive in private, but he's actually being pretty reasonable here.
The thing is, some people spend a lot of effort when writing to check that they don't accidentally leave "sharp edges" in their writing (and then they still fail to find them all) while others write the way they would talk and assume that their tone of voice is "obvious" when of course it isn't. I expect if you knew Linus personally (I do not) his most outrageous written comments would seem just fine.
There's a ton of research on how written communications (especially with relative anonymity, etc.) can lead to cascading flamewars and so forth without anyone setting out to troll or be outrageous. Linus lives in that world, so he probably offends a lot of people accidentally just as a matter of percentages.
> most successful open source project ever
Surely that would be BSD which, without Linux, would probably be Linux (and was Linux before Linux), and with Linux is still most of Linux and a good deal of Mac OS X and iOS, and without which Linux would be irrelevant.