In what adult situation is it okay to insult your guest?

The easy answer is during a roast...But that is not what I'm getting at. In an outlandishly stupid move, the President insulted the head of state of the Phillipines. The quote? "I am reminded of the great talent of the -- of our Philippine-Americans when I eat dinner at the White House." What a moron! This adds another clip to his almost endless blooper reel. Forget for a moment that he is the president, forget that he is the stolen leader of the free world, that comment should not have been made by ANYONE! to ANYONE!. But he is the president, and he is the stolen leader of the free world...and apparently he is an idiot!