Why does Elijah Muhammad teach that white people are devils?

He voiced that the white men did all the acts of the devil to take advantage and restrict the black man from reaching somewhere in their lives. They used the black man for their own purpose and winnings. They step on them to leave the black man down below. I think that it is true to an extent in some areas, but the world today is different now and I think that everybody can be seen differently. The white man doesn't want to be born as "the white devil" and keep that name for the rest of their lives. They try to change in any way possible and that is what i at least see happening in the world today.