As someone else who rides in Louisville, I can attest to the number of idiots on the road and the attitude taken by the police.
I don't have an answer. The violent methods some people are calling for will do more harm than good. The legal methods are time-consuming. Most of us have lives to live and don't have the time or money to pursue things.
It would be better if the police would do their jobs (especially in an assault case), but this is a common problem around the country, not just here.
I was beaten bloody years ago (not bike related) in Michigan, and the police did nothing. While driving, I called the police on a driver who was harassing a cyclist in southern Indiana, nothing happened. I called the police on a driver who thew a wooden plank at me while I was riding. Nothing happened.
That's life. Try not to let it bother you too much.