Yeap, there are bad actors in the police just like in all other walks of life. Do we demonise doctors because of the likes of Harold Shipman?
Demonization is a consequence of bad behavior combined with radical unaccountability.
Irrelevant. It's evidence that refutes your earlier claim that police can not legally "kick the shit out of you". They can. Dismissing them as "bad actors" doesn't change that fact.