If I am buzzed by a drone, a person in a vehicle, or anything else that causes me to fear, then it is assault, and will be treated as such, if I cannot easily flee from the assault, then it is self-defense to confront and control the assailant, whether it is a person with a gun, or a drone stalking me.

If a drone is close enough to collide with me in a matter of a few seconds, it is close enough that the operator is acting in a threatening manner.

At least that is what I will claim when some whiny kid (of whatever age, 8 to 108) complains about having to come pick up the pieces of his toy. Whether it would stand up in court or not, I don't know.