Self-defense Step #1: avert your eyes from the bad headlights. One of the problems is our eyes have a natural tendency to look at things which are blue at night, on account of our eyes' hyper-sensitivity to blue light.
It was sort of happy accident that early incandescent bulbs were low-blue sources of light that put out vastly more of the safe portion of the spectrum (infrared, red, orange, yellow).
Self-defense Step #2: screen out excess blue light. I wear polarized yellowish fit-over glasses at night. They help a lot. I found my current preferred pair at a clearance apparel/home goods store for $8. My backup glasses are yellow safety goggles -- these turn the bad headlights greener than the polarized goggles, but I've tended to use the polarized ones since I found them. You can spend more on "swannies" [0] or whatever, but I'm happy with my $8-$11 yellow glasses.
This was inspired by a HN comment, who told about wearing orange glasses to walk his dog: https://news.ycombinator.com/item?id=14170975 My first set of orange safety glasses cut out too much light -- great for dealing with headlights, not so great for noticing pedestrians.