Here you just disputed your entire thesis. Why would poor whites "want to" vote against their own self-interest? For a more complete refutation of your argument, see my article below. In the meantime, I will leave it to W.E.B. DuBois, writing long before there was Fox News, explaining the irrational division between white and black workers carefully planned by capitalists:

The "united fight" of "white and black labor" DuBois advocated "failed to work because the theory of race was supplemented by a carefully planned and slowly evolved method, which drove such a wedge between the white and black workers that there probably are not today in the world two groups of workers with practically identical interests who hate and fear each other so deeply and persistently and who are kept so far apart that neither sees anything of common interest."

- Black Reconstruction in America, ch. XVI -

https://qcp.medium.com/the-myth-of-white-privilege-6645ee9924f7

PS: There are, indeed, plenty of "Black people turning into" racists and xenophobes. Enough to pass racist and xenophobic ballot initiatives, such as the anti-immigrant Prop 187 in California.