Would you shoot someone holding a camera on the edge of your property for allegedly violating your privacy? Probably not- the state would probably take that up as murder or manslaughter. With an RC copter, it's about the same distinction -a nuisance, but was it necessary and lawful to shoot it down?
Can you determine that a moving RC vehicle is recording you from a couple hundred feet away? Those cameras are awful tiny, lately. Though, once downed you'd be able to see the camera and claim your privacy was being violated, even if you weren't *truly* aware of it at the time.
I suppose it depends on the state in which the shooting occurred. I could see this swinging from unlawful property damage to the drone (urban area/blue state) over to self defense/trespassing (rural/red state).
I get a strong "shoot that varmint down" vibe from this thread. That's a vestige of the old days, the time when people had to fight off bears, coyotes and Indians. This ain't the same thing.