I do not agree with the Nowak et al. article in every respect and will articulate some of my disagreements in subsequent posts. For the moment, I want to stress how alone you are in your statement about group selection. Your view is essentially pre-1975, a date that is notable not only for the publication of Sociobiology but also a paper by W.D. Hamilton, one of your heroes, who correctly saw the relationship between kin selection and group selection thanks to the work of George Price. Ever since, knowledgeable theoretical biologists have known that inclusive fitness theory includes the logic of multilevel selection, which means that altruism is selectively disadvantageous within kin groups and evolves only by virtue of groups with more altruists contributing more to the gene pool than groups with fewer altruists. The significance of relatedness is that it clusters the genes coding for altruistic and selfish behaviors into different groups.See earlier post for links to replies to Nowak et al. by Dawkins and others.
David Sloan Wilson on kin selection and group selection
Open Letter to Richard Dawkins: Why Are You Still In Denial About Group Selection?