In a way I understand what Sen Warren meant, although I do disagree with her. It's just that we all seem to hold Obama to a higher standard. Not because he is black, but because he was so good at the job! And because he seemed to hold himself to a higher standard as president.
And now that we're faced with the disaster that is Scrotus, emotionally we need to be able to look to a former president as proof of the dignity of the office AND the belief that 'this too shall pass' and that come 2020 we'll elect a dignified, qualified person to lead and represent the US.