Getting kicked off the service for rejecting too many rides/being a jerk to passengers and getting low ratings/etc won't change human nature. It'll just change the nature of people who drive for Uber.
I'm fine with racist people having trouble finding jobs. Or only being able to take jobs where they don't have to interact with other people. If you can't make a person less racist, marginalizing them so they do less harm is the next best thing.