I mean pigs are much cuter and nicer and more intelligent than police.

Dogs (as used in animal farm) might be more accurate except most dogs don't want to start trouble and murder brown people.

Most cops may be bastards, but there's plenty of bastards that aren't as fucked up and evil as cops.

At the end of the day, it doesn't get more derogatory than "cop". But sometimes I like to say "uniformed gangster"