No, Trump did well with that one. I mean the police brutality since. Some of the crackdown has been against innocent people (see, for example, the person run over by a horse). He never mentioned it. Instead, he had the cops disperse a peaceful protest so he could have a photo op, which was a stupid move. Trump also can't run on law and order that well, because it ceased to function under him. It's not a great argument for an incumbent. I am nowhere near certain about how this election will turn out.
that would be a better argument if Biden didnt offer to pay rioters legal fees in public....