I don't think the op can really do anything about this situation.

having said that, i will admit that i sometimes find those "car-headlamp-on-a-bike" lights a little annoying, maybe even obnoxious. but my commute is reasonably well lit, and those kinds of lights are probably overkill. either way, it's always just a slight inconvenience, and i never have to stare into those tiny suns for very long anyway. I don't get why somebody would actually ask you to turn your light down, as if it really mattered that much.

my 0.02.