Your logic is unsound, by such reasoning, which implies the only way to be safe is a safety, fails because even safeties fail, can not be fully engaged etc..
So really the only way to stop this is to not allow him to carry, that is the result of such logic.
A cop should absolutely know not to finger a trigger. That is the crux of this issue.
Safeties imho provide a false sense of security and when seconds count result in a failure of the Tueller Drill
It doesn't imply the only way to be safe is a to have a safety on the handgun. It's not the "only" way.
But it does expose the scenario where the safest gun handler in the world can have some inept cop shoot them in the leg because that inept cop doesn't "keep their booger picker off the bang switch". The odds are that having a safety would have prevented Fumble Fingers the DEI Hire from shooting him.