I’m 64 years old and have attended a mainline Protestant church my entire life. In all those years I’ve only seen known one instance where someone came to the church looking for aid, who we felt was a potential threat. I happened to be in the office that day along with the secretary, and I was able to keep control of him verbally until an officer arrived. The situation never came close to being out of control, and we probably over reacted anyway.
If this is the type of environment in such churches today, I’m glad I’m not a part of that, er, culture.
The fact that you have been part of a “mainline Protestant church” may be exactly why you have seldom seen any threats. It is the churches that are not mainline, that are nondenominational and specifically invite in the homeless, broken, drug-addicted, poor, foreign-born, and problem-plagued that tend to have troubles with security. For these people are those who most need help, and they are also the ones most likely to attract danger.