It's frankly disgusting how many people in this thread are willing to embrace prejudice as soon as it's prejudice against a group they don't like. Turns out that the lesson people learned from years of social pressure to not pick on minorities wasn't "prejudice is wrong", but rather "ok we can pick on groups but just not these ones".
We shouldn't pick on minorities because the attributes that make them a minority have nothing to do with anything worthy of scorn or... well, anything negative at all.
Police extensively abuse their power, and even the so-called "good" cops rarely speak up against their fellow officers when they do awful things. It's not prejudice to state established facts and patterns of behavior.