I think if the people having shoot outs are so brazen that they can do this and people aren't necessarily reporting them it's not a stretch to think that they will, just for fun, attempt to shoot down a UAV. Wearing a mask or course to protect their identity. Or try to damage it while it sits up on the pole with a rock etc. (Although I guess it could be protected from that fairly easily).
Another form of protection: they'd be less likely to shoot at something that shoots back. (Good luck making that legal for a private company though, even if the UAV managed 99% non-lethal accuracy!)
I think UAVs are impractical for other reasons (why not just put cameras everywhere instead of a fewer number of mobile cameras?), but I still don't think they'd be that much more a target for destruction than the electrical grid.
Doesn't have to be the thug shooting it down. Can be a pain in the ass bystander in the hood or someone with a baseball or rock. Have you ever seen kids who throw sneakers up over electrical pole wires in the inner city?
"they'd be less likely to shoot at something that shoots back."
Absolutely positively not going to happen.
I know of army units that have a machine-gun-the-RC-planes day for fun.
If only there was a device which could be affixed to the barrel of a pistol which could reduce the decibel level associated with the firing process... ;)