This is what white supremacists and racist are afraid of: As our country becomes a minority majority, they are afraid that the racists ad white supremacists are afraid that the previous minorities will treat whites as badly as they have treated them. As vicious the racists and white supremacists become, the more likely that their fears come true. If the white supremacists had intelligence, they would be as generous in opening up our society to the minorities to prevent such a backlash.
This "takeover" by brown people is nothing new. Various humans have been invading the next valley, island, country for thousands of years. We are such shortsighted beings that we don't see that this is the way we operate. Run out of game, water, women, well just head over the hill and take the neighbor's assets. The USA is a relativly new country and it would not surprise me if very soon we'll go crashing down into something else as far as the country is. I give us 20 years at the outset and you'll not recognize this place.
White supremacists are racist, hateful assholes. They are afraid of losing power.
White supremacists are driven by fear, and they are too damn broken and stupid to address that fear except by means of a gun.