Is ideology what makes a black man a black?

According to Leftists the litmus test for whether or not you're an authentic black man is if your ideology is Left. Otherwise you're an Uncle Tom and a sellout. EG> Herman Cain is in the running for Republican nomination and is blacker than Obozo as anybody with atleast one good eye can tell, but he'll be labeled as inauthentic by the Left because Cain is conservative. So apparently in order to REALLY be black, you need to be a leftist. If I was black I would find this mentality of expected group think among blacks as insulting my intellect.