I don't think a "civil tone" is necessary; directed anger can be good and helpful. The problem with Linus is that he just smears it around aimlessly, adding lots of boring noise to what may have been an interesting technical argument.
You both seem to be unaware, that emotional responses are not universal. A swear word in a second language and a different less sensitive culture doesn't feel like much to cause anyone to care enough to roll their eyes.
(I am merely trying to illustrate that we are all creatures of habit)
In a world in which there are only two people communicating with each other, you're definitely right that the point he is making can be made better. But consider that he just made his point to thousands upon thousands of potential contributors, because the message was shared. This directly addresses two of the things I hear open source maintainers complain about: it discourages the giving of shitty things and it moves away from the poorly scaling one on one communication.
I also feel like we see every single abrasive Linus email hauled out of context to make this point that he's an over-dramatic asshat, and not the mountain of mundane ones where he isn't torching somebody to make a point.
I take it you don't really read a lot of Linus' mail? I find it hard to believe that somebody would think that, unless they only got to see a highly biased selection of his emails.
Also, consider that we would never have had this thread in which several people are learning about gcc's documented behavior on unions if it hadn't been for the somewhat strong language. It serves a genuine purpose.