Well, imagine this scenario in real life: you and a couple of good friends are discussing a serious, heavy, complicated situation that you are all very much involved in. Someone you don\'t know at all wanders over and shares a friendly greeting. You eye him or her a bit, reply in a manner that suggests this isn\'t the time for such things, then try to carry on. But the person is persistant. So you reply with something akin to \"We\'re in the middle of a rather private discussion, excuse us,\" and move a bit.
Not unrealistic, no?