Under the usual rules, trolls are to be treated like zombies: they emit messages, but their words don't reflect what they actually think, but a sort of fake-thinking designed to deceive you. Or they are outlaws: responding in good faith towards them is considered bad behavior, under the "don't feed the troll" principle.

"We are actors; we are the opposite of people. So? We need an audience." — Rosencrantz and Guildenstern are Dead

If what you care about is arriving at accurate beliefs about the world under discussion rather than about the social intentions of the discussion participants, it might be best to declare that trolls don't exist, but obnoxious people do. That it doesn't matter whether a poster believes the words they're posting, but it does matter whether they are a pain in the ass.