It boils down to this:
If you think the mohel has a right to do as he pleases to my child without asking my permission whether I would this possibly dangerous practice that a small minority of people view as a chiyuv, then that is that is the strogest reason to support the city forcing mohelim to ask permission, to protect them from these dangerous mohelim.
If you think the mohel should ask permission, then you agree with the city