Yes, yes, and yes. (I might have missed an additional 'yes' in there.)
People can, and indeed do, use factual labels in order to build a narrative and either enhance or deny perspective. Some could (and do) call Brown a 'violent felon' in order to disparage his character so as to imply he deserved what he got regardless of the facts of the actual shooting. Others could (and do) call him a teenager in order to marginalize his agency in all the events. Others use them as possible explanations for state of mind and establish range of likely actions based on past actions. In short, there are valid and invalid uses of even factual labels. Some people are even using 'black', 'white', and 'cop' in these same ways. So people trying to build one narrative will get push back by people using factual labels to either deconstruct that narrative, or build one of their own. It's not all poisoning the well and ad hom or the like, but some of it is. We have to do the hard thing and actually take the arguments on their own merit, and not dismiss them because there are invalid similar arguments.
I'd call the police who arrested the reporters in the McDonalds many impolite things, thugs included. I've seen police in total called all that and worse. Hell, I saw someone unironically using the argument, 'I can't lock someone in my basement, so why can the police?' They didn't get the joke. There are a few people I have as Facebook friends who are constantly posting anti-police things. Some are fair complaints, but most are ******* insane (yes I need to trim my list). I suggest that people who believe that the police are generally all thugs, bullies, dumb, and racist go out and become police to change that. Somehow, they don't support that suggestion. But these invalid complaints about the police in total don't excuse the actual institutional problems that too many departments have, nor the large criminal justice issues this nation faces.
Of course the reason there isn't as much discussion on these police is because next to no one is defending them. We don't have people calling them gentle giants, or great family men, or the like to excuse their bad behavior. We have had I think one poster here defend their actions and try to minimize them. I disagree with that, but it's also not going to generate much discussion.
EDIT: The point I was making at any rate was that one could object to the way a label is being used, but to object because some don't consider a factual label factual is pointless.