What do they gain from causing such discomfort to others?
They might not believe so very seriously in their own ideas? (I never met a flat earther)
Most people play some kinds of irrational games to generate emotions they are addicted to. The difference is what kind of emotions they want, and what kind of scenarios they use to obtain it. There is a popular book on this topic called "Games People Play", strongly recommended.
From the psychoanalytical perspective, all these games ultimately are sick attempts to indirectly extract symbols of love, when people are too afraid of a more direct approach (aren't we all sometimes?).
The recipe for this specific game is that I cause you discomfort, and if you continue interacting with me anyway, it means that you have forgiven me (for causing you the discomfort), which means that you care about me (otherwise why would you keep interacting with me). So I frustrate you in order to extract a costly signal of caring from you, so that I can feel loved for a moment.
Why not a more direct approach? First, I am afraid to ask whether you care about me, because you might say no. Even worse, if you said yes, I would still be suspect that you are lying; maybe you are just being polite. But when I cleverly extract forgiveness from you, if you stay with me regardless of the discomfort I cause, then I can be sure that you genuinely care.
Of course, the damage caused to both sides by this approach is obvious. But sometimes people just don't know how to do it better, and any symbol of love is better than nothing.
You have a lot of control over your own mind and emotions, so don't relinquish it to malevolent tricksters. And if you can't do that quit social media. but really everyone should quit social media probably.
Yes, was trolling with my cat sometimes, as a child, she got angry, it was fun (but I stopped when I grew up)
> these feelings can follow you around for days vexing you and bringing you back to that negative state of mind. and that is hilarious to [the trolls]
Good point, I've felt those feelings indeed (and maybe the cat too)
Agreed that social media can be like that, and also, it steals time