I mean that they'd been told they were stupid-- too stupid to get respect from smart people and/or could only expect to be harassed for being stupid. And when I say "told", I mean active efforts to lower their status, not an abstract proposition.

If a person whose been treated that way accepts that they can't function well and/or will be treated badly, they're going to have a lot of background anger which can get foregrounded if they think about taking part in an intelligent community, even if it isn't actually hostile to them.