1. Your contention that trigger warnings help people with mental illnesses in the way that electric doors help people in wheelchairs is completely overstated.I'm not even talking about undiagnosed medical conditions yet.
In a first-year class of, say, 100 people, how many students do you think will have a diagnosed mental health condition that needs some sort of accommodation?
... and then think about how the same course could could have 3 or 4 separate classes in one term, and then be offered twice a year. That's like 600-800 people a year just for one course... but people like @PureX argue that it isn't worth the prof's time to identify which content warnings - from a standard list the school develops - apply to reading material they ought to already be very familiar with.
2. Evidence that trigger warnings help people with mental illness is mixed at best.
3. You would be better served to read the article...or investigate the issue more broadly...than skim it and stick to your position because it feels right to you.