Accidental discharge - maybe. Negligent discharge - definitely not.
Everyone "should" drive safely but cars are still made with bumpers, air bags, seat belts, crumple zones, collapsing steering columns, safety glass, anti-whiplash headrests, fuel and ignition cut-offs, etc.
A handgun owner would be well served with a handgun with a safety because there are Didn't Earn It (DEI) hires littering police departments all over the country.
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