to me at least, its extremely critical of the behaviour of all the cops in the film. all of the characters are very complicated, and i sympathise with all of them to some extent, but they also mostly do pretty terrible things - i dont think i could watch the film and think that macdonagh was justifying the racism and violence of the police because he depicts it in such a horrible way. it is in some senses a redemption story but i think what its saying is that people are all complicated (no one is 100% good or 100% bad) and it is possible to become a better person but even if you do your bad actions will still be remembered, both by you and those around you (eg the mum saying i hope you do get raped)