I can't help but wonder why you think someone honking a horn has anything to do with you using a bike light. Even if this were true, why would someone driving a car with 4000 lumen worth of front lighting complain about a single 600 lumen lamp? I drive for a living. If I blared my horn at every car with SUPER bright lights ( shining directly in my face ) I'd have calluses on my hand from beating on the horn all night.

I used to get cars toot their horn at me every once in a while when riding my bike. Judging from the smiling faces and waves I figured it was someone just trying to say, "Cool bike/lights, I can relate". Matter of fact on a couple occasions people have wound down their windows and actually told me how much they like my bike/lights. On the other hand if I'm riding on a road with two way traffic with no other cars around and an approaching car flashes his lights; that I usually interpret as my light is too bright. HOWEVER... sometimes people turn their high beams on not because they are being blinded but because they want to see something strange on the side of the road ( ie...you with a bike / light ).

Matter of fact I used to get people turn their high beams on ( on approach ) all the time. Now I turn my lamps on high ( in response ) and immediately get the vehicles to low-beam. Rarely does anyone continue with high-beams. ( *note, usually I am only running about 300-500 lumen, except for going down hill. )