From (now Pope Francis) Cardinal Bergoglio’s 2010 book On Heaven and Earth, now available in English.
When I speak with atheists, I will sometimes discuss social concerns, but I do not propose the problem of God as a starting point, except in the case that they propose it to me. If this occurs, I tell them why I believe. But that which is human is so rich to share and to work at that very easily we can mutually complement our richness. As I am a believer, I know that these riches are a gift from God. I also know that the other person, the atheist, does not know that. I do not approach the relationship in order to proselytize, or convert the atheist; I respect him and I show myself as I am. Where there is knowledge, there begins to appear esteem, affection, and friendship. I do not have any type of reluctance, nor would I say that his life is condemned, because I am convinced that I do not have the right to make a judgment about the honesty of that person; even less, if he shows me those human virtues that exalt others and do me good.
At any rate, I know more agnostic people than atheists; the first are more uncertain, the second are more convinced. We have to be coherent with the message that we receive from the Bible: every man is the image of God, whether he is a believer or not. For that reason alone everyone has a series of virtues, qualities, and a greatness of his own. If he has some vileness, as I do, we can share that in order to mutually help one another and overcome it.