That professor was clearly wrong to dismiss the student, and perhaps he or she might have mentioned beforehand that there is violence and sexual assault in Ovid, but that’s as far as I’d go.So, Coyne would go as far as giving advance notice that their might be troublesome material in the selected readings. Or, put another way, we might say he'd "warn" his students about content which might "trigger" them.
But a "trigger warning"? Heaven forfend!
Given what Coyne agrees would have been appropriate, I confess its no longer clear to me what he thinks a "trigger warning" is. But you can be sure that the ensuing 10 paragraphs will explain why -- whatever it is -- it's the beginning of academic fascism the likes of which threaten the very foundations of the American university.