For epilepsy we have well-justified reason for warnings. For all the other things you mentioned, trigger warnings are wrong approach. What people tasked to cure PTSD will tell you, is that you want constant exposure to the stimuli until your brain starts to ignore it, and not constant evasion.

Trigger warnings are also harmful because they legitimize the idea that you can be offended about pretty much anything you like and therefore such content should not be published. It enables people to behave like children, instead of grownups. Mature people don't get offended because someone says something they don't agree with.

EDIT: What I mean is the danger of those utility monsters you just referred to downthread.