How do you know the cops didn't think it was a real gun?
He explained it several times. Most air guns sound nothing like real guns when fired (they sound more like a stapler).
[YOUTUBE]https://www.youtube.com/watch?v=xCzpFcZXZgY[/YOUTUBE]
Cops know what real gunfire sounds like, given they all have heard it thousands of times. So, the sound of the air gun being fired is actually evidence given to the cops that the man does not have a real gun. Seeing an air gun fired would make any rational person less afraid than they were when first seeing the gun held.
Pointing this out does not imply anything about whether cops generally are quicker to shoot blacks than whites. It just means that the dogmatists trying to claim that the air gun being fired should have increased the perceived threat have it ass-backwards.
There are far better arguments to be made to support the OP's conclusion. It's just dishonest laziness to denying the obvious fact that the sound of the airgun would likely make any cop aware the gun was not real.