Such a belief is explainable by racism....you know, that unthinking, irrational, reprehensible position of basing one's evaluation of other human beings upon their race, rather than their actions.
I submit that the pastor who called in to the show was a racist, and that such racism is very common among a group that supported Obama, in both 2008 and 2012, with over 90% of their votes.
Yes, racism is alive and well in America - only it's NOT the racism that the media endlessly trumpets. There IS a group that is unable to see past skin color....and it's that group with the same skin color as Obama.
This is unfortunate - every bit as unfortunate as the historical type of racism that is a stain on this great country's history.