He should take a lead from Drew DeVault. Drew frequently says things people (including myself) disagree with and is working on software a lot of people (including myself) are very skeptical of. Yet if you try to interact with him (as I have), he's a totally reasonable and pleasant dude.
The "community" in this case is in fact not a community at all, merely a loose set of people who's only common characteristic is having an opinion on systemd. A reasonable user of SystemD, like myself, has no power to coerce a complete stranger who sees fit to email Lennart a death threat.
The "community" cannot stop this. Either Lennart should work on how he handles such criticism/abuse, or Red Hat/IBM should hire a communications professional to insulate him from the outside world. Or he can keep the course and suffer the inevitable...
It's not right that he receives death threats, but the response to that unfortunate state of affairs needs to be realistic.
I'm not talking strictly about death threats, calling him random slurs already is too much and has happened on HN, this "loose set of people" should not, and it'd already probably change his opinion about different communities. Lennart should absolutely sometimes choose his words, like Linus, but I don't think we should be excusing insults with saying "it's unenforceable" when most places haven't really tried to remain civil due to personal beliefs.
What do you expect "the community" to do, downvote anybody who speaks harshly about him? That won't stop it, and even if it did it still wouldn't stop 4channers with anime avatars on github from trolling him constantly. There is no community solution to Lennart getting his feelings hurt. That's not an excuse, it's a cold truth.
There is little in this thread which even gets close to approaching incivil. And every time the systemd guys talk about online abuse, they always mention the worst of it, the death threats and other abuse from 4chan. Even if HN outright banned anything other than glowing praise of SystemD, that would not make a difference.
I'll reiterate: the notion of 'community' in this discussion is borderline meaningless and any attempt to govern it will fail for exactly that reason, and therefore any solution to the problem of SystemD developers feeling besieged that is predicated on governing the 'community' is, frankly, worthless.