In Pope Benedict's first Encylical (an authoritative statement on church doctrine), entitled "God is Love", which also made clear that the church has no desire to govern states or set public policy (and should instead build strong consciences in individuals), he wrote that:
Love is free; it is not practiced as a way of achieving other ends. . . Those who practice charity in the church's name will never seek to impose the church's faith upon others. They realize that a pure and generous love is the best witness to the God in whom we believe and by whom we are driven to love.
Obviously, the Pope is not the only voice who speaks for Christianity, and he certainly doesn't speak for all faiths. But, he does speak for about half of the religiously affiliated people in the United States, and his reasoning in this Encylical would be uncontroversial among a large share of Christian groups that are not Catholic as well.
Many commentators were puzzled that the topic was chosen when he "could easily have delved into a more problematic issue." But, Benedict was not throwing a softball here. Threats to Catholicism to the right see Christianity as a religion focused on hate. Threats to Catholicism on the left bemoan a church that sometimes seems indifferent to social justice. Benedict is trying to pave a middle path of consensus.
As a non-Catholic, I don't use the same reasoning that Bendict does, but I come to the same conclusion. Charity is a moral obligation and should not come with strings attached.