Metal detectors do not violate state laws. I don't read anything in 65.870 to say that metal detectors are illegal. Local governments can legally control concealed carry in their buildings. It would be pointless to have a metal detector to find openly carried firearms. Also, 65.870 makes no mention of other deadly weapons that would be metal that local governments can control all they want.
I would be behind you 100% if you were pushing for laws making the right for self defense carry all over the state.
I would be behind you 100% if this could only be used for illegal acts of our government
I would be behind you 100% if they were using this to do illegal acts
But as it is I see nothing illegal about having metal detectors to search for weapons, what they do with that information is another thing all together.