If that is your lens, then the answer is that the police behave this way, the authorities behave this way, the police are militarised, because of some sort of psychological propensity to racism.
Yes, that makes a lot of sense of some of my experiences trying to talk to Americans about some of the shit that goes on over there arises. Any attempt to understand how this stuff happens tends to be treated as a why question, and answered with "because they're racist." It was immensely frustrating.
A poster tried to make the point that if you swapped "men" for "white people" in Bergdorf's initial comments that it would all be fine
I don't think this is strictly speaking true.
I've certainly heard some women propose that men are born sexist; they're not. They're born into sexism. There's a difference. Equally, in America everyone is born into racism because it's endemic among their culture.
There's a difference between men/women and white/black though, in that white skin does not confer an inherent physical advantage; the advantage arises because of what skin colour means in a racist society. Thanks to sexual dimorphism, being male does confer an inherent physical advantage, and sociocultural wossnames permit and encourage men to capitalise on that advantage. So while there's merit in the comparison, it's not a perfect fit.
And yes, I do object when I hear women saying all males are born sexist. Our sons and brothers are not born this way; we (collectively) make them this way.
Random aside relating to earlier in the conversation: I was today years old when I learned that Barbary corsairs were coming up the Channel and carrying off white British people as slaves as late as the sixteenth century. The Americans did for them in the end, when the slavers started going after American ships. I gather they were fairly thorough about it too.