If you're saying trigger warnings are mostly political (I think ideological is a better label but whichever) that is a different topic. The issue in debate here is wether or not, regardless of any social or political baggage, they have some actual utility. In the case of PTSD or depression w/ suicidal ideation, I think they do. Suicide is, in fact "contagious" in it's way. Letting someone make an informed decision about such content can literally save their life. Similarly, PTSD isn't something really helped by repeated exposure to a "trigger". What you propose in terms exposure to get used to the world is the psychological method known as flooding. It does help with phobias, but generally is not effective treatment for PTSD. Part of the treatment path includes minimizing exposure to known stressors while other treaments have time to take effect.

In short, your ideas here appear to be shaped by your politics, and they simply doesn't match up to mental health best practices for effective treatment.