I'm not sure how this conversation changed to talk about police brutality, but I think the argument is that if there is a bystander watching or recording, the police officer can later be identified.

Compare to a situation in which identification is not required and the officer can't be identified even with video evidence.

But with all the smartphones around, someone can get the officer's badge number hopefully while they're beating you.

I don’t think we’re discussing police brutality here, not that it isn’t terrible and more common than it should be. I live in King County and every week it seems some person assaults another for little to no reason (often with a hilarious number of priors) and walks the same night. That is the violent crime that isn’t prosecuted here that the GP was referring to.

Smartphones don't have the resolution to pick up a badge number.