Because that's an outright lie and I have absolutely no doubt that you know that. I suppose "Hillary blaming sexism for not winning" is accurate, even if woefully unrepresentative, since she did reference sexism in the attacks against her and, probably accurately, said it was a major factor against her candidacy. But at no point was even a meaningfully percentage of the left, let alone "the entire left wing" claiming anyone who opposed Obama was racist. While racism obviously did play a role in resistance to Obama (birth certificate/Kenyan birth, Muslim, race war, "deep hatred for white people," globalist, etc.), I think the primary reason for unreasonable disdain for him was the product of stupidity and reliance on right-wing con men and profiteers, not individual racism.