I don't believe those were terminal values. If someone changes their position from pro-segregation to anti-segregation, I would expect that in their previous model, segregation seemed better, but later they updated their model, and under the new model, segregation seemed worse. Better and worse in making everyone happy, for example.

Some people sincerely believed that segregation brings better results for everyone. Whether they were right or wrong, segregation was just a means of achieving some other value.

EDIT: I think we should be careful about assuming that our opponents have different terminal values. More likely, they have a different model of reality.