I've long been sympathetic to ideas like this - I remember as a little kid, blowing off the big stigma around the (then-novel) 3d shooters that had just come out, like Doom. Ironically I agree with exactly what you said, but simultaneously think you might miss something in the analysis. I think that maybe a better way to phrase the idea is:
In the rare case that you're positive for a trait, you can be incited to it by stimuli.
For example, if you have an anger-management problem, you can live quite peacefully, left alone, but you are uniquely dangerous to provoke. Behaviors and stimuli that are harmless to other people cause a violent outburst from you. Same thing with alcoholics and, for example, pedophiles - stimuli that provoke no negative behavior from other people will provoke it in someone positive for a trait. Violent media left us with a tiny driblet of actual killers because only a tiny fraction of people are positive for a trait of being stone-cold killers.
--
So what are we afraid of? We have barely any actual killers. We're afraid of enablers.
We have a tiny, tiny group of people that will dare to do crimes (say, shooting up a synagogue) when there are clear and present consequences for it. I'm quite sure, however, we have a still small, but much, much larger group that are "latent" trait-positive for violence. They'd do it - if they could get away with it.
What we're really scared of is a third group - which might be a group so large that it could be anywhere from 30-60% of our society. People who could be coerced into not caring about the violence. That third group is the people who are trait-positive for gullibility (and several other related traits). I think it could very well be "most people" - a plurality if not a majority.
These are what enable horrible things. People who have bought into propaganda really don't do anything, and that's exactly what's so horrible about them; because they don't express some sort of obvious, negative externality in their neighbors and coworker's lives, nobody really cares if they believe horrible things. Because they don't really "act on" those beliefs - they don't go out and do things that hurt people.
But they also don't intervene when a crime aligning with their beliefs is perpetrated.
And that's what's so scary.
When a black man would get lynched in the old south, the real thing that made it possible was the hundreds of other bystanders who felt like the black guy deserved it. If they didn't exist, such a killer would rapidly be brought to justice. But instead, since so many were okay with it (and even cheered it on), not only would the killer get away with the act, but quite a few much more "minor" trait-positive people participated in it - people much less naturally driven to kill, but who could work up the courage to do so if they could get away with it.