I don't waste my time 'flashing' those that drive with them on. However if I see someone that's obviously driving with their hi-beams on I'll give 'em a quick one to let them know, just in case they care. I don't see any reason to get into a flashing war, that would just result in doubling the amount of idiots on the road.
If your lamps are foggy spend a few minutes and clean them up. There are plenty of how-tos on the subject here.
BTW, just because you have a car that sits in a truck's beam pattern is no reason to drive with your fog lamps on - get real. You have the option of using the night-glare adjustment on your mirror. You picked a car low to the ground just as they picked a vehicle that wasn't. Maybe one, both or neither of you feel that the other picked a sensible vehicle, but that really isn't the point, is it? Nobody's being fooled here or on the road.