I agree, that's definitely part of the problem. "Closing ranks" to protect each other is, I think, an inherently loyal and noble response, but it has to be tempered by humanity and reason, and that does not seem to be happening.

There is probably also a strong element of fear- as mentioned in the article, many of these police really are trained in aggressive response, and that becomes both muscle memory and instinct, it genuinely does.

I think many great officers imagine the "what would I have done" and in their doubt and worry over that hypothetical, provide a unified front against the repercussions of justice for their fellow officers, in case the same should ever happen to them.