You're overreacting here. This is not a safe space issue. The discussion still takes place, it just comes with a content warning.I'll wager the students are expected to read the relevant works prior to lecture, so it shouldn't be out of the blue. I also don't think it's unreasonable to expect college students - especially at a place like Cambridge - to have alreadyu developed some fortitude and emotional resilience.
College is not a safe space. In fact, it's (supposed to be) the exact opposite. College is supposed to be a place of open discussion and dialogue, where people are repeatedly and aggressively challenged intellectually by both their instructors and their peers. Sometimes that's uncomfortable, and that's a good thing. It's supposed to be.