Current-day Linus wouldn't react much differently. Cut the "shut the fuck up", the one or other "fuck" (but not all, some need to be there for emphasis), done. It's the real personal shit, the "should be aborted retroactively" stuff, that he cut out. "Obvious garbage and idiocy" is a technical term, programmers apply it to their own work all the time. Compilers are more technical in their language but we know what they mean.

And was this mail, seen in its total impact, a hardship? He went down hard, yes, and thousands upon thousands of Linux users breathed a sigh of relief, seeing that Mauro's attitude towards userland doesn't fly.

The hardest-hitting sentence in that mail is actually "You have shown yourself to not be competent in this issue". Absolutely devastating. Taking context into account it's the equivalent of telling a professional cook that their ingredients suck, what they did with them sucks, and most of all that the gall which which they claimed that the customer is wrong about their dinner sucking is completely, and utterly, unprofessional.

Of course that's hard on Mauro. There's no way to tell someone about such an epic cock-up without being hard. But not going that far, avoiding that hardship for some notion of civility, now that would be right-out cruel.