That actually doesn't surprise me all that much, all considered.
The kind of morality that Dawkins is talking about is the shallow utilitarian-behaviorist version of "morality" that the ~Rational Community~ has long tended to gravitate towards. If one takes that perspective, then yes, obviously the prospect of supernatural reward and punishment is going to have an impact on one's actions. Utilitarianism is all about human actions as rational responses to incentives, after all.
At least I can respect this argument coming from Dawkins, since it's consistent with his intellectual premises. On the other hand, people who claim subscribe to an orthodox Christian theology and parrot these lines of argument are making a mockery of their faith.
That we see Christians propounding this type of argument points to a major failing in catechesis in this country, and one that has been important to the decline of religion in the United States. About three-quarters of Americans say they are Christian, but a far lower proportion has a grasp on what that means. If you have been raised into a secularized mindset, it is easy to adopt secular apologetics that seem convenient to the theist position at first blush, even though they undercut it in the long run by implying a materialist paradigm denuded of spiritual power.
Agreed.
Now I would posit that for most secular people there exists er... tension between their ethics and cosmology/anthropology, but nothing about that stops them from acting morally.
This. People, especially those who are secular who reject an absolute and transcendent source of moral truth, are often far more influenced in behavior by their cultural environment and basic biological impulses than whatever views they have concerning how morality is grounded and whether it exists at all. Even the most consistent moral relativist will be outraged if he heard a child was being sexually abused. One needn't have a coherent, consistent account of why murder is wrong to know intuitively that it is evil and to refrain from it . For this reason, the God/morality debate often ends up in a logjam, since there is a difference between having true moral knowledge and acting on it vs. actually being able to ground it.
