No one is implying it is ok to be a jerk while flying a drone, we all agree we need to use discretion and common sense in any flight. My simple point was to try to direct the thread back to the original question that is the title of the thread “Is it legal to destroy someone else’s drone”. If someone does “react” by throwing rocks or otherwise attempting to destroy the drone their reaction is illegal. Drone pilots do need to be responsible and respectful, just as we should in the rest of our lives, but if a drone happens to enter an area that annoys someone, the drone is not fair game for target practice.
Addressing the separate topic that flying that close to people is illegal, that would not be true in the USA, here it Is ABOVE people that is prohibited, the OP stated he was not above any people or train, but again that is another discussion. If he was flying illegally a call to the authorities would be in order, not attempting to take the law into their own hands by destroying the drone.