Lets say you have a dad and he murders and rapes a bunch of women. Should you be punished for his crimes in any significant way? No! You are not your dad.
Lets say you have a great great grandparent and he enslaves a bunch of blacks. Should you be punished for his crimes in any significant way? No! You are not your ancestor.
But all the pro black people won't change their minds because they have a party to stick too. My mind is free!