I ride 95% on MUPs, and on a warm evening such as last night when there are lots of people out commuting and exercising, I can easily see other bikes and peds that have lights (even on dogs), and find it very difficult to see bikes and peds without them. If they are difficult to see, it logically follows I'm more likely to hit them, thereby injuring them and myself. Therefore, it I conclude that lights make everyone safer.
I run two 700 lumen lights (bars and helmet), and if aimed up, I can see even the ninjas, but since I have to keep the lights aimed down to avoid blinding others, more often than not they appear out of nowhere at the last second. I don't think anyone can make a rational argument that lights do not increase safety. It's kind of obvious if you ride at night.