Actually, the following is the source of the dustup. Dan Scavino of the campaign saw this tweet and thought the quote was from Coburn, which it was not. It was from the writer of the article, who later quoted Coburn's other quote, the more reasonable one in the body of his article.
Scavino later removed his original tweet and replaced it with the story regarding Coburn's actual quote. Trump was on the road and in meetings all day in SC, and may not have heard about the mistake or misquote. Though I have no way of being certain about that.
I agree Trump should apologize, if for no other reason than the contrast he will provide with Ted the Face of God.