I don't think you'll win this one. You're completely correct, but you'll probably only end up convincing them that no one should have a gun. What denomination is this?
Right now, the proposal is all or nothing. If the congregation does decide to ban all firearms, to include LE, then that would be in direct conflict with the synod; as well as disarm those LE already members of the congregation.
I like my church and am hoping that those who have supported such an action, will either see the light, or leave themselves. In any case, I need not find another place to worship.
Oh, ELCA = Evangelical Lutheran Churches of America.