I took a History and Philosophy of Science class in college. Fascinating class, taught by two professors, and a very odd pairing at that!
Anyway, one of the classroom exercises was to develop a "strategy" for interacting with one other person in the class. You either cooperated, or you defected. Points were awarded to people based on whether they cooperated or defected, based on what the other person did:
Both cooperate: both get one point
Both defect: both get no points
One person cooperates, the other defects: The cooperator gets no points, the defector gets two points
Point of the exercise was that an inherently "friendly" strategy (i.e. you're cooperative all the time, as long as the other person is also cooperative) resulted in the most points for everyone involved. People who occasionally defected, while they might make short-term gains, still did not earn as many points as pairs of people that had friendly strategies.
That case can be expanded to what Dennett is talking about here. Morality is good because civilization provides the maximum benefits for any given human. Defecting (being immoral), while it may give short-term gains, is not as beneficial to a person as morality is.
That was a great interview, good link. I think I got a better understanding of determinism/fatalism out of it.