Jno: With respect, you don't seem to think that I understand the origin of the prejudice, which I'm pretty sure I do (though obviously if I don't then I'd appreciate correction): people can see instances in the past where the police have deployed violence against people disproportionately and unjustly, and are thus suspicious of them. That's not really something I have a problem with.
What I have a problem with is people (and, yes, some ABers) who appear to shamelessly take on that suspicion and from it immediately pick a side in any controversy involving the police before any facts have even become apparent. And then think they're being really savvy. Even the most basic, fundamental, back-of-the-mind rational instinct should take issue with thinking like that. It is simply stupid - a word which I hate using, but I just can't think of anything else which describes it.
Personally I would much, much rather attempt to make a judgement intelligently and be wrong than make a stupid one and happen to be right.