I would like to say, while I'm generally not too sure how I feel about trigger warnings, that when I had my abortion in college and went around telling my professors what was going on, one English professor proactively looked at the syllabus, told me the next class was going to be about Death and that maybe I would want to miss it. I would have gone and I wouldn't have been triggered by the lecture, but I really needed time, space, peace, and to be with myself at the time. I was so, so greatful he did that for me. To me I guess that is the way a trigger should be dealt with. A student who maybe can't handle something should get a private, considerate "heads up" from the teacher, and the student can then choose to participate or not. If I had triggers I would not want the entire class to know about them, I think it would make it worse.