Their skin color doesn't define the type of men that they are, and doesn't solely tell the story behind their relationship, and why it ended. Nonetheless, he's the past, he's not there anymore.
Would you still want to live in America if slavery ended a year earlier than 1865? Nothing different in the modern era. It literally makes no difference, that was over a hundred years ago and every human alive during that time is dead.
Her previous relationship is an ex and will always be an ex, and you will probably never see him except for in a picture somewhere, and maybe not even that. He is the definition of the past, and will stay right there where he belongs. If they were meant to be, he wouldn't be an ex. That being said, if you're willing to judge her for her previous relationships, then you don't deserve to be in her future either.