Should You Shoot Your Son?

If you want to be polite, probably better not to use had better. Because it tends to imply consequences if the advice is not followed. So for example, imagine you get a phone call which you're not expecting when your son is on holiday in a strange foreign country and you hear this message. They could say, should you shoot? Or they could even say, you must follow our instructions, but had better implies if not what we're going to kill him.