Richard John Neuhaus on why religious organizations which provide government-subsidized social services should be free to prosyletize:
"The legitimate interest of government is in seeing that the social services for which it contracts are effectively provided, and, if the providers want to tell people why they're engaged in good works, that's their business. It should make no difference whether the providers are faith-based, faith-saturated, or atheists. The last is an academic point, of course, since, for some reason, there are few atheist charities."
Neuhaus is correct, of course, not only about the paucity of atheist charities, for which the reasons are not mysterious, but also about the right of faith-based charities to discuss with their beneficiaries the motivations for their benevolence. It's no business of the state's whether these organizations seek to persuade people to join their fellowship or not. The state's only concern should be whether the services being paid for with tax-payer's money are being duly provided.
As for the dearth of atheist charities, one need only ask why, in a godless world, anyone should care about the poor or the infirm. These people are the losers in the Darwinian lottery and there's no obligation to artificially sustain them. The obligation to care for the poor is imposed upon us only by God, not by nature, and it is out of love for Him that we love those He loves. If God doesn't exist then other people have no claim on our compassion or our purse, and there's no reason for us to not turn a blind eye to their suffering.
Indeed, if God does not exist then Sartre was probably not far from the truth when he noted that hell is other people.RLC