From my experience (not all of it, but a bunch of it) -- HR has been the balancing force against bad management and even CEOs because, like the lawyers, there're there to protect the company. I've not been in a room where the CEO is sitting there telling the lawyers and HR how to abuse employees -- sorry.
Likewise, I agree there are plenty of cops who are POS, and there are plenty who are not. You're missing the part of the equation where people treat all cops like POS, and frankly -- if you've watched shows like COPS and seen what some of them deal with -- it's not hard to see why some of them probably become worse over time.
Both sides of the equation needs to change if you want a better world.