First of, 90% of the reason I posted this was become it ended with "whatever they're least wrong about." I do not think it necessarily stands up to intense scrutiny.

That said, cooperation is only valuable as an intermediate goal, yes, but I think it's a pretty damn important intermediate goal. If both sides are defecting, nothing gets done. Don't forget your most important goals, but go for them strategically in a way that doesn't burn all your good will.