See the post above yours, it explains it. It’s about keeping out of the church out of the jurisdiction of real cops.
Having said this, awhile back, somewhere in the middle of Iraq war, a few of my fellow members started to carry. I live in Texas, so having an AR15 in the truck in the parking lot was common even before this. I started to carry a few years back when I found out that Allah Ackbar translates as please shoot me now! We have a couple of law enforcement types and a few firearm enthusiast that I suspect carry. Out of maybe 100, I suspect 10-20 are carrying.
There have been many crimes in recent years in churches that don't involve the pastor running off with the piano player or a Sunday school teacher touching a child in the wrong place. If you have such a large campus that you need more than a few deacons carrying, I can see the use of a security force in charge of several campuses. If you stop and think about it, we risk what you are talking about everywhere. Cities can cover for hijinks in the mayor's office and college campuses can cover for the Regents. Selective enforcement is possible anywhere, not just a church. What would make a crime in church somehow more devastating than a cop covering for the chief stealing from the evidence room or a jailer using a broom handle to sodomize a prisoner?( which has happened) The guys that I know for a fact carry in church can shoot, but I don't know everyone that carries. Having a trained force sounds a little more secure to me. The only caveat now is I will continue to carry no matter what. Perhaps a few years ago, I would have left it in the parking lot. I've learned the difference from 1960, when you left your doors open and the keys in the car, to today, where 8 different organizations want to cut your head off and dance on your burning body. I may die anyway, but I would rather die with a gun in my pants than hiding under a table while an idiot picks us off one by one.
The telling thing about what you said was you trust churches less than you do a city or a college. Personally, I don't trust any of them but most churches aren't pits of crime and if there is wrongdoing, it's usually some guy sucking women's toes or some other repressed fornication. If a church cop decides to cover up for a pastor stealing money or whatever else, surely he would shoot back when a Muslim comes in to spray the church. That's the bottom line in this story.