What was the motive of voters and politicians who supported segregation?

[Intell]

I mean in the north, there was an attitude of black people can be equal, they can be president, but they better not live next to us, or date our sons and daughters. To be fare this was not done only against black people but every ethnic group didn't want to live next to teach other etc.... There was a lot of insular self-segregation in the north.

This was true from the upper class to the working class.