"We are not to look to what men in themselves deserve, but to attend to the image of God, which exists in all, and to which we owe all honour and love. […] Therefore, whatever man you meet who needs your aid, you have no reason to refuse to help him. […] Say he is contemptible and worthless, but the Lord shows him to be one to whom he had deigned to give the beauty of his image. […] Say that he is unworthy of your least exertion on his account; but the image of God, by which he is recommended to you, is worthy of yourself and all your exertions. But if he not only merits no good, but has provoked you by injury and mischief, still this is no good reason why you should not embrace him in love, and visit him with offices of love. […] We are not to reflect on the wickedness of men, but look to the image of God in them, an image which, covering and obliterating their faults, should by its beauty and dignity allure us to love and embrace them."
– John Calvin, Institutes of the Christian Religion III.vii.6.This is a very interesting point Calvin makes: that the basis for loving my neighbour is not lost through my neighbour's unworthiness, or even active hostility towards me. I am to see in my neighbour the gift of God - that God has seen fit to make even my broken and destructive neighbour a means by which others might see something of the divine life.
Of course, none of this makes sense until we learn to see Christ as God's image, into whose likeness we are drawn by the Spirit. The ever-open possibility that my neighbour might conform more closely to Christ's grace and truth keeps open the door to treating her graciously and truthfully. None are beyond the transforming power of the Spirit of Christ. All are vulnerable to grace. I love, then, in order that my neighbour might become more fully herself by becoming more like Christ.