If one, for instance, lets a door slam in someone’s face, an apology is in order.
But to apologize for the enslavement or murder of millions of people is to trivialize that offence and reduce it to the level of a social gaffe.
Acknowledge, yes, but apologize?
Apologizing for something you neither did nor caused, or allowed to happen is meaningless. Apologizing on behalf of someone long dead is also meaningless unless you are certain that he would do so if he could.