Jeannie Suk Gersen:

If, in the face of scientific findings, one lets go of the view that trigger warnings foster mental health or facilitate learning, what reasons might remain for using them? It may well be that, at this point, trigger warnings have developed a spinoff cultural meaning that departs from the aim of providing psychological aid to those who suffer from trauma. A trigger warning might really function as a signal to the subset of students who are looking for it that the teacher is sensitive to their concerns — or at least compliant with their requests — regardless of psychological benefit or harm. The choice to send such a signal is of course part of a teacher’s academic freedom. But it is important to undertake it with the understanding that signalling compassion for students and trauma survivors in this particular way may be at cross purposes with helping them, whether psychologically or pedagogically. 

Yep.