I don't agree with your take.

Dark themes are to make you feel sad or down. Nothing wrong with that. Kids playing this game are murdering people. So I don't think protecting the kids is also the right answer to this.

It is ok to feel offended or sad in a story, they are not feelings we should look away from, and I don't know your mental state, but it is your job to protect yourself, we can't give warnings to every little thing that could bother someone.

I did get a chuckle with the word trigger though. Fitting in this case.