Why do black American blame whites for the start of slavery when their own people sold them to us?

This is a very controversial subject. However, most agree that black Americans blame the white for the start of slavery, even with knowing their people sold them, because many whites today still benefit from the damage done due to slavery back then. Many also believe that this generalized blame is because of the fact that because of slavery many white families had more opportunities that have continued to allow them to prosper throughout the years.