I've found myself contemplating the idea of things being "triggering" a lot recently, because of a friend withdrawing from my life on the basis that seeing me was triggering.
Gosh that must be painful @Manicsfan
As I understand it, people with genuine PTSD or who have genuinely been through harmful experiences, can be triggered by things that might appear to be random. That is, unexpectedly, and not necessarily always a replication of the actions that harmed them originally.
I'm from a much more stiff upper lip generation, but I was once violently mugged in my street (just a few doors from my house) - I was beaten about the face until I was so off-guard that the mugger grabbed my bag. I cam through the experience, although there are still situations/people I will cross the road to avoid.
I found myself thinking "Well that wan't too bad. At least I wasn't raped." (typical female minimising male violence, I guess).
But a few weeks later, I was in a gym circuits class, and one of the stations was a Boxercise type station. I found I just DID NOT want to do that - having been beaten about the head, I just couldn't do it, even in play/training. So I told the instructor this, and I've told instructors and my personal trainers ever since. I don't do Boxercise or combat style classes at the gym.
But I don't demand that my gym stop holding Boxercise classes, nor do I hyperventilate watching others do sparring etc on the floor of my gym.
I suppose I was 'triggered' in that gym class, but I dealt with it like a grown-up! And it was a pretty minor triggering in the scheme of things.
But pedagogical research suggests that "trigger warnings" are not necessarily effective, and we can't really predict what will trigger people who've been through trauma. I think also that part of being a responsible grown up is trying to deal with the after-effects of trauma, and get on with one's life. Although I realise this is very dependent on one's material circumstances. Very dependent.