I have heard some competitions/ranges banning the Serpa holster. IMHO this is a user problem. Bad training. Every person carrying a gun period should live by this rule. Finger at register until ready to fire. I have never even heard of a person using this rule with a negligent discharge. If your finger is on the trigger you better be aimed at your target already. Banning the holster is like blaming the gun for an owner who shoots himself while cleaning his weapon. Still the gun owners fault.
"The spirit of resistance to government is so valuable on certain occasions that I wish it to be always kept alive. It will often be exercised when wrong, but better so than not to be exercised at all." ~Thomas Jefferson