There is no strictly historical perspective that leads to denialism. It is fundamentally tied to antisemitism and providing ammunition to modern day fascists and racists.

Sure, but surely you can be a fascist without also being violent? I mean surely you can be a communist without supporting violent revolutions...

I don't believe that you can. The core belief system of modern neonazis is the protection of the white race by excluding non-whites. It takes violence to remove non-whites from their nations. And then, because of the one-drop rule, the ratio of white people will always drop across time. This necessitates violent responses. All neonazis agree on the goal and there is just one means to possibly achieve that goal: ethnic violence.

You’re pretending that all political goals can only be achieved through violence.

No I'm not. Many political goals can be achieved without violence. Creating a white-only nation is not one of those goals. That one specifically necessitates violence and this makes neonazis fundamentally violent.

Do you honestly believe that if the neonazis were in charge that I'd be given speech rights?

From what I understand the violent rioting is a small minority and distinctly not the objective of the greater BLM movement.

Holocaust deniers turning out to commit hate crimes, encourage violence, and going on to aim for violence towards minorities is well-documented to be a significant proportion of that group.