In truth, the defect implied by the coming of the Lord in human form was more basic: Our human nature was bent, like an overburdened clothing rod. More than smiles and politeness and observance of duty would be necessary to fix it. And, in earthly terms, it really could not be "fixed," not just yet. Faith in the Little Lord Jesus was a sound step in the short run, but it would take his resurrection and return to dispose once and for all of the "bentness" problem.
In the meantime, Christians would be ... people. Of a certain sort, naturally. But, still, people. Not always "nice" to others, not even nice, all the time, to fellow Christians. This was notwithstanding the commandment of the Babe, grown to manhood, that they should "love one another," as he had loved them. They would try. But -- sigh -- bentness often would block the way.
Over the centuries, the physical achievements of Christianity -- the hospitals, schools, universities and missions -- as well as the deeds of mercy, forbearance and sacrifice would surpass all logical expectation. At their very best, the people of the manger -- Christians -- would speak of themselves as the redeemed, bearing a message of redemption "which shall be to all people."
The stumbles along the way, the falls, the catastrophes, would remind them of the human mess over which the angels hovered on that silent night: not in approval or confirmation, rather, in love of the wayward humans into whose midst a savior had come. To whom, that is, Christmas had come.