While I do think that the terms "trigger warning" and "safe space" have been overused to the point where they've sort of lost their meaning, I think this letter misses the point of them. Yes, people shouldn't use them as a form of censorship or preventing students from getting exposure to alternative viewpoints, but shouldn't a student who has been a victim of rape at least be given fair warning if a class is going to cover literature that includes a rape scene, which could bring back actually traumatic memories for them?
There are certainly cases in which these should be used, though of course, they shouldn't be overused.
Exactly. I think this letter was written to gain publicity, not for any other reason.