And the other important thing to note is that even if they are dealing with it with a professional, they will recommend that they try to avoid things which could 'trigger' them (so read reviews about a movie before watching in case it contains a graphic rape scene). This is because getting over issues like PTSD, fears, or anxieties, requires a gradual desensitisation to the material under controlled conditions and preferably with an expert there. Forcing people to view material that could trigger them without a warning is essentially a process called "flooding", where you simply force them to deal with their issues by dumping them in the deep end of their problems, and this unsurprisingly has the effect of setting back any progress made and often making the problems worse. So it always seems strange when people say that we shouldn't use trigger warnings because people just need to "deal with it". No shit, but part of dealing with it includes being able to prepare and compose yourself for possible upcoming triggers. Trigger warnings are just society's way of saying, "Hey, if it takes a tiny note or 2 seconds to mention something that might help you avoid having a debilitating and horrific attack, which would set back your mental health progress by a significant amount of time, then I'd prefer to do that".Yes, but the way to do so should be handled by a professional, like you said.
And that's mainly because the people who most often get angry about trigger warnings have never experienced the kind of psychological trauma that results in someone having a complete and total loss of their faculties when triggered. Shit, I didn't even realize how serious this shit could be until I spent time in a mental hospital as a patient.