churches should have security guards, just like every other massive group of people that assemble.
You don't put 5,000 people into a stadium for a coldplay concert and not have a shitload of security. Why put thousands into a church (I have attended some that are huge) without a few quiet, disguised security guards?
We cannot assume the sanity nor intentions of anyone. Churches are a sacred place of worship for those of us that attened - but can be nothing more than a soft target with many elderly for a shooter.
Add more armed guards. Opens up more jobs too. They can hold doors too. Even better, I bet many of the parishioners are retired military or police that'd do it for free just to help out.