All this said, some people just pick the wrong damn game.
If you have severe issues with graphic depictions of violence, but you choose to play Werewolf, I'm going to stare at you. Same for Vampire, especially if you've got severe issues with depictions of submission, control, objectification, and I would go as far as to say psychological abuse. Ghouls are an integral part of Vampire, especially on MUs. I knew someone who'd been kidnapped, and they really wanted to play Changeling. They lasted two days. Two days.
If you have things that trigger you, really know the game you're playing, because those things might be integral to theme, some in glorfying ways (violence, usually), some in condemning, but still hard to process ways (kidnapping, psychological abuse) and sometimes... casually, which can sometimes be the worst.
That said, I think every game does a good job of outlining these themes in the books and if you read the books and think you can handle it, more power to you--but I don't think "violence" is a tag needed for a scene centered around werewolves, for example.
Beyond that, on a MU you're going to have to deal with other people playing their shit in public. A werewolf player isn't going to stop and ask, "is everyone okay if I pose tearing this person apart?" And a vampire player isn't going to not treat their ghoul like an object (if they would IC), nor ask if it's okay, in a public vampire space, where that's the cultural norm.
I'm all for trigger warnings and what not, but there is a context. You can choose not to play a game whose themes directly take you to your trauma.
BTW, "But in real life you can choose to never leave your house, too," is a stupid comparison and I am saying so before anyone makes it. These things are not comparable in scope or meaning.