Really sorry to hear this is happening in the US now too. It is a very common practice here in SE Asia and Police sets up checkpoints to get paid.
Here they simply find things that are not right with your car or motorbike or want to make you pee for drug tests. They basically hassle you until you pay. As longer as you are not paying as higher becomes their bribe.
Alea iacta est ("The die has been cast")