Two big issues have already been made in the other comments- the problem of anonymity, and the "don't feed the trolls" solution. I'll touch on the first issue only to say that I came up with a name for it a while back, and a I'm stupid proud of that name: ring of Gyges effect. Story of the ring is worth looking up, I think it sums up the issue nicely. Okay, that's it, others have already pretty much walked that ground.

As for DFTT- I've been wrestling more and more with this one recently. From a practical standpoint, I agree with TNG. Trolling invites its own distorted dopamine feedback wherein pleasure is derived from antipathetic response- be that the good ol' downvote (how many can you wrack up for a single post? -thankfully this one isn't an issue in these parts) or else the vitriolic reply. This being the case, the best practical deterrent to trolling behavior tends to be a lack of any response whatsoever. On a purely mechanical level, it works, and I've espoused it in the past. Especially here, where sporadic troll outbreaks have threatened not only the overall tone of the site, but the integrity of our response as a community- we tend to place great emphasis on being decent people interacting in decent ways. By responding in kind to trolling attempts, we kind of belie our adherence to the notion that we're all human and ought to respond to each other as such.

This invites a moral quandary, though, doesn't it? In what other environment are we encouraged not only not to respond angrily to bigotry, ignorance, hatemongering, but rather not to respond at all? if we're to treat interactions online exactly like face to face interactions, why are trolls exempt from reproach? Maybe it specifically discourages trolling from our neck of the woods in the short term, but might it also be at a certain point tantamount to refusing to speak out against The Big Issues more broadly? In the wider world, doesn't lack of meaningful response mean being Part Of The Problem?

I don't yet have an answer to these questions- I still think the best way to off a troll is to pretend he isn't there. This has been demonstrably effective in the past, at least in this venue. Besides that, I'll continue to advocate for human decency no matter what- even if someone seems hell-bent on stirring the pot, I try to remind myself and others that we don't actually know the motivations, life situation, social standing, etc of the person with whom we're interacting. While somebody might come off as just arbitrarily nasty, they might be bogged down with all sorts of real-life baggage, of which we're only seeing the leather trim. That doesn't mean we have to agree with them or take their views seriously, but it does mean that we ought to respond calmly and with as much empathy as we can muster. Rational debate is hard, as you've demonstrated with the above examples, but it's not impossible. It's also absolutely vital to this arena in particular, and important most of all when we're confronted with something hateful. After all, decency is easy when you're among friends. Much harder when antagonized. That's when it's worth the most.

So long story short: regardless of motivation (which we can't divine or else justify), be decent, and in so doing: 1) maintain your own personal integrity, 2) take a vocal stand against that which ought to be stood against and 3) give the trolls insufficient fuel to keep trolling. That's the best I got, so far.

Good post, by the way.