It's actually pretty simple. It's just based on observable reality. Observation: some whites appear to hate themselves, and non-whites are happy to accomodate this mental illness, since they lose nothing by gaining an advantage over another tribe. There is no reason to expect that the whites who hate themselves will stop hating themselves when they become a minority, so the tribal warfare should be expected to only increase, going from an ideological to a material stage.
Should be mentioned when I say "whites" I mean "people of European descent", which puts into context what this all really means.
This can all seem rather surreal until you look at countries with balkanized populations. These ethnic minorities in their own countries where they are majorities show no desire to treat minorities particularly well, so why should we suppose an alliance of these minorities against a european minority will show particular restraint? I realize this hurts some people's world-view, this idea that everyone (except the evil white colonialists of course) is deep-down a good and benevolent being, but ignoring reality will not make it go away.
If you want a picture of what the future looks like for a european minority, just look at how they are treated in areas where they are already outnumbered. How are ethnic Assyrians doing in Syria? What about Christians in the Middle East? Are they treated with overwhelming kindness? If not, do we suppose minorities in the west who have been taught by the media that whites are uniquely evil, will show an especial kindness towards the new minority?
Let us remember those sacred words: "White piggu go home!"
Oh whoops, there is no longer a home? Well, shucks. What a shame.