As someone who has been dealing with these issues for the past two decades, hearing the same, first-year undergraduate arguments about God's existence, about the nefarious social influence of religion, and about the possibility of a secular ethic is really quite tiresome. Yet, at "On Faith", Sally Quinn gives space to Herb Silverman, who founded and is President of something called the Secular Coalition of America. Wow, how counter-cultural.
As to the first, that is God's existence, my response anymore is, "Who cares?" God's existence is no more dependent upon some kind of argument deemed "rational" or "logical" than is the existence of gravity, evolution, or second law of thermodynamics. Whether or not an individual, or a whole planet for that matter, believes in God or not no more renders God non-existent than a refusal to accept the evidence for evolution somehow renders the theory invalid. Most first-year undergraduates who take some kind of survey class in western thought run up against the same arguments Silverman offers here. While they might be exhilarating to an 18-year-old who is hearing them for the first time, their novelty wore off a long time ago.
As to the question of "belief" and its social dimension, I cannot imagine an issue for which I care less than perhaps the previous one. All social phenomena have both good and bad aspects, religion among the rest. Since Silverman has no idea what he's talking about when he speaks of belief, as it operates for Christian believers at any rate; since Silverman seems to think that Christianity is the sum total of religious expression in the United States (odd, considering his surname), his argument is nonsensical from the get-go, because other religions define belief, and the content thereof in completely different ways, and live it out in ways that are alien to the Christian mind-set.
Finally, is it surprising to anyone, after nearly 200 years of doing so, that there are ethical codes that are quite successful that have nothing at all to do with God? It shouldn't be, at least to anyone who has been paying attention. Yet, to judge from the readers comments, as well as Silverman's, one finds the idea somehow fresh and new to some people. Again, it might be a good idea for them to return to undergraduate school and take a survey class in Enlightenment, Romantic, and modernist/post-modernist thought.
Like conservatives who spew out gobbledygook, the best way to treat nonsense like this is not to respond to it, but just point and laugh. When adults are carrying on a conversation, and a child interrupts, we usually stare for a moment then carry on as usual. Best way to treat garbage like this as well.