If "Pax" is speaking of the SERPA duty holster, I have seen a video clip of how it can be torn completely off a duty belt BUT...
If you watch the clip, it talks the grabber a considerable amount of force to tear the polymer holster off. A armed security or sworn LE could or should be able to deter or defend against the threat. The officer or armed citizen could also deploy a 2nd gun, OC spray or Taser/EDW too. If you aimlessly stand by & let a violent thug grab your firearm you have more problems then the brand you carry.
I'd add that the Safariland SFS or ALS may be a better pick if you feel the weather conditions or work environment(jail, prison, mental health center, court, etc) may lend itself to fights or outbursts/gun snatches.
PS: I agree to that a gun owner or sworn LE officer can TRAIN to carry & use the SERPA safely. As the YouTube.com clip of "Tex" shows, it's not the SERPA holster but Tex's improper method that caused a mishap. Tex(the victim) clearly says that in the video.