...and *also* join the rest of decent society in the presumption that groups like the KKK are self-evidently bad?
A very common manifestation is the "DEMOCRATS were the party of the Confederacy!"
Well, yeah. But *today* you're the ones defending the Confederate monuments and flags and cause. So ...?
We do this in story. Movies, history, museums, novels, etc.
Truth-telling.
And people—even people who hold similar beliefs to those groups—consider themselves good.
Therefore they are not of this group.
But those they hate are.
But I will say one other thing.
We can tell the truth about any group. Any group at all.
Now—despite vigorous efforts to the contrary—it is, for now at least.
It's not something decent good people are a part of. That's a known fact.
And everybody considers themselves good.
We should tell the truth about them, persistently and for an extended time, and in story.
We might be surprised what happens.