Well, for the question why Ninja's don't get harrassed, the answer seems to be, because you can't see them.

But I understand the sentiment. I see sooo many ninjas around here, people without lights. One time I was actually passed by some guy in all black/no lights/black bike. I caught up with him and some Japanese tourists coming out of an alley didn't see him and most have clipped him. In addition to the Ninja thing, I don't get why he was riding so fast, give people at least a little chance to see you. Obviously slowing down would have probably avoided the crash all togehter, or at least lessen the impact. I almost felt sorry for the tourists, what a way to spoil your vacation. I don't know about injuries, but it always suprised me how few deaths we have compared to the large number of riders without lights.