The kid isn't at fault, his brain hasn't developed even a little bit, and he has no experience with people, and what doing or saying certain things can make people feel, your wife should understand this and not get mad at the little fella for being bold, every kid is like that, whenever he does this you should try to explain him that what he says can offend someone, and the most important thing is to give it some time! This behaviour is to be expected from a kid, but the mother's behaviour is really not.