Perhaps those who are attracted to jobs that authorize them to carry loaded guns and legally kill people are not suited for them. Mebbe?

There will be bad examples. My ex was certainly suited. And to my best impression she will still be.

If they are attracted to the position BECAUSE they get to carry a gun and use force.... Maybe not.

I've had run ins with security guards without guns that let their authority go to their heads and tried to use extreme measures to assert that authority within their tiny kingdoms.  I have no doubt that what you say is true in some cases.