Edit:
"my kid are playing in our backyard. Do I have the right of privacy?": No you do not have a Right to privacy, I can put a camera on my roof or pole and record your backyard if I wanted and there is nothing legally you could do about it
Drones falling from the sky: General liability laws would apply no different than if I am mowing my lawn and a rock flys out and hits you, or if I am play yard Darts and I toss one over your fence which injures you.
I can not prove it is safe: That is not how a free society works, the burden is not on me to prove my actions are safe, the burden is on YOU to prove that my actions have a more likely than not probability of causing physical harm to others or their property
Other Air Traffic Hitting a Wing: Why are they below 400ft, or the less than 100 ft I would fly but still be under the FAA Regulations, My entire point is that under 100ft should not be under the FAA at all,