It always has. Or at least tried to. Despite that the Civil Rights movement achieved massive success during a much more regressive period of US society. Trump represents a swing of the pendulum that has been brewing ever since. The election of Obama supercharged this reaction and incited panic in the white nationalist segments of the population. This too shall pass.

That’s why slavery “no longer exists in the US” (up for debate). That’s not what makes it morally unacceptable. Force doesn’t determine morality. It determines what happens. Your statement amounts to a tautology: “whatever happens is what happens”

And by the way, that’s not even the whole story. The civil rights movement succeeded without force or violence for the most part. So your whole framework is pretty flimsy I think.