I don't think it's unreasonable to be uncomfortable with the idea of cosplaying cops tailing people and sticking guns in their faces, whether those people are guilty or not. Personally I think the media does a huge disservice by always framing felonious behavior or people as innocent as it just creates more divisiveness, though I suppose that's by design.
We empower cops and require them to follow a strict set of rules. These yokels operated outside of that system, and a man died as a result. The victim's actions or personal behavior are irrelevant to the violation to that system committed by the wannabe cops. Do I think they set out to hunt down and murder a black? Nope. I think they took the law into their own hands and fucked it up so bad that a man wound up dead, and that there should be a price for that so we don't have other yokels trying to crack the case wide open too.