Exactly. This is why I hate it when psychonauts push the "there are no bad trips" angle. It's a lie, and psychedelics can have a long lasting negative impact on the brain in some cases.

Following the logic, though, it could be undone with a positive experience on psychedelics...

Or you could have further triggering experiences

I'd guess it falls in the category of "don't do that", along with things like using dd to overwrite your failing hard drive with a copy of your shiny new blank drive. You shouldn't take psychedelics therapeutically unless you're set up to have a good experience, I assume.

(I've heard that expectation of your experience actually influences your experience a lot, so it could even be self-fulfilling!)