Arguing with genuinely stupid people just makes me frustrated and depressed. It's far far easier to just ignore them.
It is extremely difficult to tell apart genuine stupidity from advanced trolling.
Indeed. I'm as certain as one can be that the flat earth movement is half stupid and half troll (at least on Internet message boards). I sincerely hope that my unscientific estimate is not erring in favor of the right hand side there.
I've always just assumed that it was just "trolling", like being a follower of the FSM - noodles all round.