A good friend of mine is a pretty centrist ex-army guy. Definitely not your bleeding heart leftist. I remember one time we had a class that abruptly got pretty detailed on sexual assault--after the class, he went to the bathroom and vomited for about fifteen minutes. Turns out he'd been raped as a kid, and while he was able to remain composed during the class, the discussion was stressful enough to cause that reaction. He's fine as long as he knows that sort of discussion is coming; he prepares himself mentally for it. But it causes a problem when it comes up abruptly.

PTSD is a real and pretty common thing. Saying "we're going to discuss issues relating to sexual assault" is a courtesy that costs virtually nothing and can save people a lot of pain. Now, of course it can go overboard--people talking about trigger warnings for ageist microaggressions and the like is silly. But that shouldn't invalidate the entire concept.