Hm. I'm not totally opposed to trigger warnings when they are used responsibly. I don't think they are overused in every day life, but that is mostly because my university does not use trigger warnings at all so I don't see them everywhere like apparently everyone else does? In fact I've never experienced a trigger warning anywhere but tumblr...
The thing about exposing people to these things is, it should really be done with preparation until they are better equipped to handle the topic. Shoving rape in someone's face and saying "hey its exposure therapy, grow up" isn't going to work and may make it worse. I got triggered in class when the student led discussion suddenly and pointlessly went to the topic of rape. I full on dissociated to the point where I didn't even hear 90% of the conversation and I still don't know how I got home after that. Which is honestly just dangerous and didn't help me get past my fears one bit. If anything things got a lot worse after that. I stopped taking campus classes and actually withdrew from people so I wouldn't have to hear them talking about rape again. Of course that was before I was in therapy or even knew what dissociating was.
Now I kind of wish in some course descriptions they would at least give a warning to say "Difficult topics such as this and this and this have a history of coming up in this course" so at least you can be prepared. I think a good example of trigger warning was in a forensic class I took. Obviously I knew there was possibly going to be some gory stuff, so I was somewhat prepared. I'm like, 100% good with osteology, but I can't do fleshy stuff. Luckily this field is like 99% bone stuff. But on a powerpoint the teacher uploaded she made a simple slide describing the photos on the next one and said the pictures could be skipped if needed. So I was glad to at least get a warning to be prepared for well... nice processional shots person's decaying maggot covered flesh... and knowing ahead of time made it much easier to look.
I guess my point is, I don't think trigger warnings should be overused so students can get out of doing things, but I do see their importance as WARNINGS to prepare students to fortify themselves mentally in order to confront things that are much more difficult for them to confront than the average student. There is literally nothing wrong with that.
Now, on tumblr... that's a completely different story. I've seen people trigger warn for posts just talking about a normal day at work "tw: retail" like... thats too much.