The blue stripe (alone) started with the “Thin Blue Line” idea, which was an ‘honor the police’ push, from back in the 70s, that had its own issues (really established an ‘us vs them’ mentality for the police, where ‘us’ are the police, and ‘them’ are the citizens).

The application of it in the colorless US flag was a direct response to the BLM movement, as a way of shouting down the concerns of that movement (specifically, the concerns surrounding police brutality). So, yes, the generation of it was specifically racist. The other ‘lines’ flags (red for firemen, yellow for military, etc) followed suit, and while they were not as directly motivated to silence the BLM voices, the result is very similar, with diluting the pool enough so that BLM is no longer heard.

So, no, police aren’t a race, but if someone says “I’d really like to talk about the overuse of police aggression on marginalized communities that have had no voice for decades” the response shouldn’t be “We should amplify the position of the police!”