Yeah, we have some issues to clear up in the courts. Speech advocating the denial of people's rights doesn't have to be treated as free speech, in fact it's the opposite of free speech.
There is nothing in the constitution that tells us we must allow people to agitate for officially making groups of people second class citizens. The courts once held that slavery was legal too. We fixed that and can fix the other.
Until that's done we will just have to suppress racism by exercising our own constitutional right to assemble and shut them down one way or another.