I think you're looking for a depth of equivalence that I wasn't suggesting was there.
To further muddy things, you should know that explosions themselves don't produce the responses they do just in veterans. High-bandwidth sounds trigger an autonomic response as soon as they hit the brain stem- long before the cortex has a chance to think "I recognize that as an explosion", the brain stem said "HOLY SHIT SOMETHING IS HAPPENING". This mechanism is observed in rape and abuse survivors as well as veterans.
So in what classroom circumstances would a warning be necessary?
I'm all for being courteous, I just have serious concerns about giving college students the impression that the world around them needs to adjust to them rather than vice versa.
A warning is never required. If you are unable to listen (or god forbid a disturbing image) to controversial issues that are literally occurring in real life you won't be able to handle the real world once college is over.
These things do occur in real life. Granted I don't foresee a professor showing a beheading video in class. However, for the sake of discussion, if the class is about geopolitical theory/issues and the discussion is regarding how do we deal with terrorists. Maybe the student believes we should treat them with peace and love but has actually never dealt with this issue in real life. By all means show them a beheading video without warning to see how their opinion immediately changes.
People used to congregate for miles around to watch a good beheading. They sold beer and pastries, and people fought to dip their handkerchief in the blood of the executed. It was a grand entertainment.
Now we watch Bachelor in Paradise. I'm not sure it's an advancement.
I don't think TWs should be required. But explicit descriptions or depictions of assault are pretty low-hanging fruit here.
By not making a policy, but encouraging a culture of learning about common triggers, we also encourage a more adaptive approach. If someone is distressed and they let you know, you can decide whether it makes sense to warn about that content in the future.
To further muddy things, you should know that explosions themselves don't produce the responses they do just in veterans. High-bandwidth sounds trigger an autonomic response as soon as they hit the brain stem- long before the cortex has a chance to think "I recognize that as an explosion", the brain stem said "HOLY SHIT SOMETHING IS HAPPENING". This mechanism is observed in rape and abuse survivors as well as veterans.