While I would would not in any way want to denigrate the wonderful philanthropy of Christians, it is probably worth remembering that the two richest men in our country, both of whom have given or pledged a large fraction of their fortunes to charity, are atheists or agnostics. The Bill and Melinda Gates Foundation does wonderful work in education and health.
It's also worth remembering that they are ardent supporters of abortion "rights," and both are basically monopolists. Also, their foundations can be regarded cynically as a tax dodge and a jobs program for their offspring. I do admire some of the work of Gates with diseases in Africa. Warren Buffett is hardly someone whom conservatives should admire; he backed Jean-Fraud Kerry in 2004.