They were laughing/gasping because not once, but twice, he called the hecklers Afro-Americans (not african americans). Just dug his hole deeper for me...
Afro-American was the preferred PC/academic term in the '70s and '80s. A prefix, like Anglo-American or Sino-American. Some folks consider it antiquated, but I've never heard of anyone finding it offensive. It does not refer to the hairstyle.