"Traumatic" is a hard concept to nail down, but if it's useful at all, the victim has to decide what's traumatic in the end.
The thing is that the victim doesn't live in a vacuum. Anybody can be manipulated.
These people latch onto people who've had certain experiences... experiences that are often confusing... and also sometimes traumatic... and most often involve having been treated like crap in a major way by at least one hardcore asshole.
They usually go for those who've had the most extreme experiences, and already feel traumatized... and who have the least idea of how to approach that on their own. Then they manipulate those people. The word "groom" is not necessarily inapt.
If you don't have a strong social support network, or one that will help you with this taboo issue, then they'll give you a network. It'll be one where everybody sees things their way. They'll seem surprised, and maybe just a little disappointed, if you don't naturally buy in to most of their ideas. You'll get a ready-made set of supportive friends... at least as long as you follow the party line.
If you need a way to relate to the experience, or to part of the experience, they'll offer you an already built up, self-reinforcing framework of ideas and even feelings. They mostly truly believe that framework themselves. And of course it fits their agenda.
For the ways that you already feel damaged, they'll encourage you to nurse your sense of harm. No adjective is too extreme.
If you don't feel very damaged by some aspect they think "should" feel damaging, then they won't easily take you at your word. They'll believe, and probably tell you, and definitely silently telegraph, that you're in denial. If it's not on your mind, you're repressing it and "everybody's worried about you" (or some similar angle). Sure, you get to pick the things you feel most hurt by, but you'll won't find it easy to get away with completely shrugging off anything at all.
In every part of how you think about your experience, they'll encourage attitudes that maximize your perception of the damage. The mind being what it is, that increases the actual damage. If the victim decides what trauma is, then in at least in some part the perception of trauma is trauma. They amplify trauma.
Then we get to how you're meant to deal with that trauma.
They'll say, as a rote recitation, that everybody deals with these things differently, and they're unlikely to give you a bunch of commands. But the ways they'll assume and expect are normal or praiseworthy will be ways that match their agenda.
... and the one thing you don't ever get to do is to decide you're over it. You're persona non grata if you do that. To be truly healed is to be shunned.
They'll encourage you to make the whole thing a major part of your identity... and more so if you want to stay in the core of the club. That often comes in the form of a strange contradictory view, where you define yourself as somebody who refuses to be defined as a victim. Which still defines you as a victim, but in a way you won't have to notice.
If you've truly been hurt (heck, even if you hadn't been hurt), there are usually plenty of people you can legitimately blame. They'll try to concentrate your blame on the people they want to use it against. And they won't easily let any blame go to waste; transgressors must be punished! Or at least ritually vilified. You can always come up with a reason why somebody is even worse than you thought.
They'll "love bomb" you and bury you in praise if you get behind their public agenda. If you don't, you'll get a sort of "Oh, well, I guess it's OK. Not everybody's strong enough to fight the forces of evil and be an inspiring, luminous survivor advocate like Mary over here".
... and they'll encourage you to do all that to the next person who comes along.
You can watch them do this just by reading the news, and once you look for it, you can see it in the things they say in blogs, social media, and random comments.