He was graciously listened to, received applause, and even given a standing ovation at the beginning and end of his speech at the NAACP last week.
But when he disrespectfully referred to the Affordable Care Act with the pejorative term "Obamacare" and said he'd repeal it, he was booed for 14 seconds.
Could he have been so stupid as to blatantly tell an audience, 96% of which supports President Obama, and which benefits from many aspects of health care reform, that he planned on dumping it as soon as he's elected? Of course not.
He may have been at the NAACP, but he wasn't talking to the people in that room. He was talking to his far rightwing base, who'd be watching on TV later in the day. And the booing by the African Americans in the audience? That's a feather in his cap to his base.