I suspect that these two factors may have played a role, but the main reason for Dawkins' remarkable self-identification as a cultural Christian is that he has slowly come to realize that even the values that he cherishes--values such as individual dignity, science as an autonomous enterprise, the equal dignity of women, the abolition of slavery, and compassion as a social virtue--came into the West because of Christianity. I have been hammering this point in my debates with leading atheists, and it's possible that one of the Oxford historians came up to Dawkins and said, to his horror, "You know, Richard, that D'Souza chap has a point."
Okay, so let's give this biologist credit for learning a little history. Still, the deeper question remains. If the God of the Old and New Testaments is such a bad character, how come his cultural influence is so positive? Absent a good answer to this question, we must reconsider the premise: perhaps the God of the Old and New Testaments is not the evil figure portrayed in atheist propaganda. On the contrary, perhaps all our Western notions of good and bad derive from no source other than this Christian God. This certainly was Nietzsche's view, and he knew a lot more about the subject than Richard Dawkins.
Wouldn't it be interesting if Dawkins continues his intellectual growth and reverses his old misunderstandings? The first step for him would be to imitate the example of “cultural Jews.” Cultural Jews may not accept the Yahweh of the Old Testament. But they do tend to champion Jewish culture and defend Jewish interests, such as Israel. In a similar vein Dawkins can reject Christian theology while defending the political and cultural influence of Christianity. He can rebuke ACLU lawyers, for example, who are trying to eradicate all vestiges of Christianity from the public square. Perhaps eventually Dawkins will even reissue his book: Overcoming My Delusions: Confessions of a Cultural Christian.