I rejected all mathematics by virtue of choosing to study English

Whoa, what college did you go to? At mine we had breadth requirements which meant that even if you majored in the liberal arts, like English, you had to take so many math, science/lab, language requirements and so on.

I would agree with what you present about the variability of what's being taught in a given English class depending on the professor to a pretty significant extent. While I don't think that an instructor should completely change their lesson plans and syllabus to avoid an uncomfortable subject, it would be possible to plan an entire course gently avoiding certain topics if the professor had that as a goal when they sat down to plot it all out.

However I think that generally speaking, especially if you are likely to be the only person disturbed by a topic, the onus is on the student (or the person likely to be triggered) to privately approach their teacher (or other authority figure) during an appropriate time to talk 1:1, like during office hours, to raise the potential issue/communicate that the student is sensitive to certain topics, and instead of asking the professor to change their plans to accomodate the student, I think the student should come prepared with suggestions or ideas for how they will manage their issue. While in an ideal situation you might have a professor who will alter reading material and discussion items in order to be sensitive to a student's needs, I think it is kind of arrogant and self-centered for one person who has an issue to expect and ask that the course experience for all students be changed just to accomodate them.

I also think that such topics, and potential triggers, should only be brought up pre-emptively when it looks like that might be necessary. For instance there was a question recently, "If someone has triggers, should they let other people know about their triggers and ask that their friends refrain from discussing them?" basically asking the etiquette on such a situation. That question made me think about the subject and in short I concluded that one should try and only bring up the fact that [x] is an area of discomfort and triggering, if there's a reasonable expectation or past history that indicates that [x] is probably going to come up. If I walked around telling everyone I met, immediately, that "rape triggers me, please don't talk about it," that would come across very off-putting-ly. In addition it serves to try and make everyone bow to accomodate *me" - when frankly who knows if rape would have even come up otherwise? It is drawing more attention to the whole issue/event, and I think that's part of why some people view those who talk about triggers dismissively. Because it can seem like an attention grab.

I think if you have an issue it is up to you to manage it; much like diabetes, while I can be aware of your sensitivity and try to accomodate it, at the end of the day, the person who needs to fully manage the problem is the person whose problem it is.

If something is triggering for a person in a university class and it comes up in class, the triggered person should excuse themselves as politely as possible and return when the discussion is over or they are more composed. Personally, needles make me pass out. I've been in a psychology class watching a video when suddenly there was an injection on the screen. I immediately began to feel ill and lose consciousness. I had to be carted out of the room on a stretcher actually as I wasn't able to make it to the door, haha. But point of the matter is that I didn't expect anyone else to know of my sensitivity, I didn't blame the teacher for putting the video on, and I didn't suggest we no longer watch such videos in class. I tried to manage my condition as much as possible and when I could not I removed myself. If I had expected the situation to repeat I would have spoken with the professor quietly and we would have reached a solution. It certainly doesn't require me to run around and tell everyone I know that I have a tendency to pass out in certain situations. And I can't ask others to refrain from normal behavior "in the off chance" it'll make me pass out. My health is my responsibility. I can't blame someone else if I do not manage it properly.