Harris gets to the meat of it in #7. Morality is just plus-sum problem solving, which invariable involves broad cooperation (aka morality).

We cannot always agree on what constitutes a plus-sum outcome, in part because we have different values and in part because contingent fact - scarcity, say - affect actual pay-offs. But laws, mores, and customs internalize plus-sum policies so that we don't have to continually rediscover them.

Of course, things change, and then pay-offs change, and existing "solutions" obsolesce. But the question is always the same: is this a plus-sum opportunity? If so, the moral course of action is to participate in seizing it.