Not just your dad -- Martin Luther King was a registered Republican. Republicans desegregated the schools (Eisenhower and Nixon), They passed the Civil Rights Act against southern Democrat opposition.
Democrats gave blacks welfare, which destroyed their families. They gave them affirmative action, which destroyed their self-respect, initiative, and work ethic. They gave them Margaret Sanger's eugenics to destroy the babies of "lesser races" through abortion. They gave them unions and pro-union legislation (like the Davis Bacon Act) to exclude blacks from high paying jobs. They gave blacks a generation of double-digit unemployment.
They gave blacks a scapegoat (Republicans) to hate.
Yet blacks still vote Democrat. Stockholm syndrome much?