What speed were you doing and what was the speed limit? I find many drivers are too slow these days and drive well below the speed limit, rather than too fast (I hardly ever see anyone going over the limit or much over) and yet so many are doing a good 20k below and yep, that gets my goat. I'm one of those who will get up behind you if you're going too slow, but I never do the headlight thing - that's excessive.
Usually (but not always) the driver in front will speed up or move over to let me pass, and if they won't do the speed limit, so they should.