When Romney was born it wasn’t only Mormons who were racists. It wasn’t only members of that religion who had racist views and practices.
Romney was a high ranking member of the LDS church when their God was making people black to punish them for sins done before they were born. Romney still reveres Brigham Young. A racist who married 50 or so women. Romney still believes in a founding prophet who created a holy book by peeping at a magic stone inside his hat.