When you have stereotypical views of the world, and you are trained that stereotypes are bad, you cannot handle accepting that you have stereotypical views, so you project them to others.

They are stereotyping to an extreme degree by claiming that all of U.S. history was bad and all people immortalized in statues were just 100% fundamental evil.

At the same time, they accuse black cops of white supremacy. This projection is more subtle and it has to do with "hating your own kind".

You will notice all these people rioting or 'protesting' are white. Generalization, but mostly true. How can they decry whites and call them fundamentally evil, while being white? Self hatred.

If they have self hatred, they will project those values onto black cops.

That's why black cops can be "white supremacists".