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.
Ding. House as a metaphor for nation and all that, as well. i.e. we all grew up in a house built by slaves, and we’re raising our children in it too, get it? We’re not responsible for the slavery and racism, and we don’t approve of it, but we nevertheless benefit unequally from the fruits of it. That’s the deal with institutional racism. You don’t need any intentional, conscious racism at all to keep it going indefinitely.