How do you countenance the numerous times an actual threat like Dylan Roof are allowed to be taken into custody when a "justified threat" like George Floyd are killed in the street?
This isn't really an apt comparison IMO. Floyd wasn't an ideological killer. He was killed on the street for a minor criminal allegation. There wasn't a massive police response with the most highly trained guys in the local/state/national agency taking him down. The guy who killed him appeared to be a rather poor cop (or at least he was around controversy a lot). It's apple to oranges to use these big mass shooters with guys killed like Floyd was.
I suspect Roof probably wanted to be taken alive (manifesto, etc.). A somewhat better comparison would be someone like the Dallas and Baton Rouge cop killers. But again, both were killed while still shooting at the police (or having very recently done so). There are some apples to apples white/minority comparisons you could make, but I don't think the facts verify racial prejudice (Chris Dormer/Tsarnaev/Nidal Hassan/DC Sniper).
Anyway, I think this argument misses the point. Anyone who seriously analyzes how high profile takedowns and captures occur will likely acknowledge that racial bias doesn't play a major role.
I think the better question/argument is "why will the same minor drug bust be far more aggressive with a black perp in Baltimore than a white perp in the suburbs"? I'm sure we won't see entirely eye to eye on that either, but I think it's the right question to ask for issues with American police brutality/racial disparity.