Those who oppose trigger warnings like the commenter above you, who believe that you should be ready to handle anything a piece of fiction throws at you. After all, it's just fiction, right? Generalizing, this usually comes from people who have never experienced deep trauma or at least who have never confronted it. Or possibly they have, but they were lucky enough to have an upbringing that gave them the tools to remain mentally stable while doing so. They also tend to be low in empathy - they believe everyone has a mental state similar to them so they can't understand, at an emotional level, why other people would need trigger warnings. For them, quite reasonably, trigger warnings are annoying spoilers and they dislike that.

Then there's the people who support trigger warnings. Often this comes from having experienced deep trauma without a support system (internal or external) that was strong enough to deal with it. Or they have observed this in people they love. These people know how fragile mental health is for many people and they want to start building a more supportive society, one small part of which is adding labels to fiction that will let people know when dangerous traumas might be triggered by reading it. And undealt-with traumas are dangerous - they are the basis for all kinds are dark behavior which I won't list here.

And then there's me. I just don't wanna read about sad shit. Give me happy fantasies man, not that dreary misery loving suicidal bullshit.

(Or maybe I'm in the second group but I've reached the denial stage)