I read an article here on Medium some time ago (apologies, I can't put my hand to it now), where the author talked about a guy that flew the Confederate flag because he was a proud Southerner. The guy in question was a student at some university or other, and the author of the piece (IIRC) was a lecturer at the university. The author/lecturer approached the Southerner/student and said something like:
'I've gotten to know you over the semester, and I know you are proud of your Southern heritage. I also know that you don't have a racist bone in your body. However, people who see that flag, and know what people usually mean when they fly that flag, will assume that you are racist and won't take the time to get to know you as I have had the opportunity to do. I think you are doing you and the South a disservice by flying that flag."
The upshot was that the student stopped flying that flag and found other ways to represent the South positively.
It seems to me that, the same is the case here. 'Back the Blue' has been co-opted by racist thugs (or those that benefit from some police officers being racist thugs), in much the same way that 'patriot' has been co-opted by those that want it to mean (or be a cover for) white nationalism. It's time to come up with a new slogan that can't be co-opted by bad actors. Maybe, to steal a line from KRS:1, 'Officers not Overseers'.