Bernie Sanders sometimes speaks in artful code so he doesn’t have to own up to what he’s actually saying. It’s one of his less endearing traits, and here he goes again.
What he’s really saying here is that President Obama and Hillary Clinton don’t have a genuine bond of affection and respect. That the woman who served as his Secretary of State isn’t really his friend, she’s cynically using him like a chess piece to attract black voters.
As Oliver Willis says, why wouldn’t Hillary want to embrace Obama’s legacy?