The flip side I've heard is that LE doesn't arbitrarily slow down arrests due to a difference in ideology. It seems more simple than that. Who wants to go through the effort of making arrests if the DA is letting them free. The LEO will see them commit the same event the next day. I don't think anyone would want that in their day to day job, much less law & order.
It's like writing a PR/MR every day [by hand] and having it declined every day, eventually you stop.