Stupid people are dangerous because reasonable people can’t predict unreasonable behavior. An intelligent person can understand the logic of a bandit, because the latter is at least rational. The bandit wants personal benefit, and since he cannot think of win-win situation, he will harm others.
But, if you are rational, you can foresee the actions of a bandit, and build up your defenses.
It is impossible to do this with a stupid person, who will harass you for no reason.
Usually, the stupid person catches you by surprise. Even you are aware of the attack, you cannot organize a defense since who you are attacking has no rational basis for their behavior.