I don't buy the idea that he didn't know what it meant either.
His mother was a French colonial in Africa---the words "macaca" and "macaque" were often used by French colonials when reffering to dark skinned Africans. It was their equivalent of the n- word. I am sure he probably heard her say it when he was younger.
His move in saying that to a dark skinned person videotaping his speech was downright idiotic.
I know that Czar Nicholas II used those words to denigrate the Japanese, as well.
I'll bet she was startled to see them out in force in Virginia hunting her and her son down.