There was an interesting post from Scott Alexander about this from the long long ago, about how bad cases provide higher signaling value. As you say, when the police are being legit evil, it's not worth complaining about because everyone agrees with you. Only a TRUE BELIEVER will argue for the release of triple-murder-rape home invader illiterate crackhead dindus.

https://slatestarcodex.com/2014/12/17/the-toxoplasma-of-rage/