It's always redneck types like this that think its a good idea to approach someone's vehicle and berate them. Also, they seem to fear phones more than anything, as they may actually have to be held accountable for their actions.
I had something similar happen to me not too long ago. A guy was going about 30+ over the speed limit in a giant van, nearly hit an old woman who had to swerve to miss him, and didn't use a single signal when jumping across multiple lanes. I took a picture of his tag with my phone and he did not appreciate it very much. Got out of the car, came up to my window, and got incredibly upset that my phone was out instantly. He got a picture of MY tag as some sort of "own" on his part, but obviously it didn't mean anything. He too was wearing a shirt with his business name and phone number on it, so I did some research and the guy pulls about 200k a year with some BS contracting service he owns. Lucky guy.
Not gonna lie, I'm in AZ and I have a BLM hat in my car (no sticker) that I bought from a Veterans charity, not knowing the meaning(don't judge me, I thought it looked cool). I leave it in there for a little extra insurance in case I get pulled over. As a Vet myself I normally don't have any issues, but you never know.
As a Vet, you should probably not feign support for a group of individuals who genuinely do not give a shit about your contributions to society, and actively work against civil rights. Blue Lives Matter is about as racist as they come.