Trolls, themselves, don't tend to believe in listening to everyone.
They're certainly not looking for debate.
To them, a discussion is not even about uncovering a truth or—more unsubtlely—being right or wrong.
It's about winning or losing.
From a troll's perspective, all interactions are a game with a desired outcome: winning.
In order to deal effectively with trolls, you can't even let them play their game.
As someone else pointed out, trolls might not be strategic in their interactions.
They want to inflict pain and hurt—and will do whatever action enables their pursuit.
This is why I call this a "game".
It may not be a literal game like Monopoly but the effect is the same: a zero sum outcome for which they hope you will lose.
But just because a troll may lack foresight, doesn't mean you have to.
It's worth asking, "When this person talks to me, what's their goal?"