It isn't his "African" name that's the point of contention. If his name were african, the idiot right-wingers wouldn't be playing their silly little games with it.
But the point is, his middle name is a middle-eastern name. (Note to fear mongers: it's just the name his mama happened to give him, not a sworn allegiance to a philosophy or a religion.) Fear-mongering and xenophobia are some of the most effective tools that the conservative talk-show cretins have in their arsenal, so those are the tools they use the most. Unfortunately, their audience either prefer to have their views provided to them, or are not quite bright enough to see the game being played, for what it is.
They make very thinly veiled accusations that if his middle name is Hussein, then he is obviously a muslim terrorist (and the cretins take it and run.)
As for the "outrage" that he would wear native garb when visiting a foreign country, I guess some people on the conservative-reactionary side would conclude that an American showing customs courtesy to foreign dignitaries actually
is insulting to Americans.