I assume the meaning is that even Michelle Obama, descendant of slaves, was benefiting from racism insofar as the house she was living in was built by slaves.
Maybe, but what you want to do? Knock down a perfectly usable White House and waste money building a new one, just so we can say the President no longer lives in a house built by slaves? The White House was built by slaves. It was wrong, it was racist, it was a crime. But it is too late to reverse it. The While House is already built. Nothing can undo the fact that it was built by slaves. The slaves that built it are long dead, there is no way to help them, there is nothing to do that will do any of them any good. Make sure it is remembered how the White House was built, build a monument to the slave that built there. Put up a plaque to remember it. But it is done and can’t be undone unless someone invents a time machine.