Things are so much better now.<quoted text>
Families fled based on a fear that going to school with black children would be harmful for their children. The specifics took a a variety of forms. Some feared that educational values would be sacrified. Some feared violence--either due to your "primal" view or due to black/white agitation. Some feared loss of control if the school population changed.
Recall that the basis for school segregation to begin with was to ensure a favored status for those who had always been favored. Desegregation threatened that favored position.