Some cars like the smart have a sharp cutoff on the headlights. When you hit a bump the cutoff line goes a little higher making the other drivers think you have flashed your highs at them, so they flash their highs at you and you flash your highs at them thinking they are telling you your highs are on. It is just a big circle of confusion.
The best thing to do when they flash their brights at you is...
Nothing.
Now, the actual problem is the fact that the car has a stiff ride and the headlights bounce a lot, so the fix is to get a smoother suspension or ride on smoother roads.
This is also why I will not "upgrade" my headlights,

it will just make the problem worse.