I would say that the above is not theoretical nor is unproven ahead of time. The state of current society (with all its warts) is a testament to the feasibility (and one could almost argue inevitability, from a survival of species viewpoint) of the morality underlying the co-operative model -- if all humans were indeed the hyper-competitive a-types or the free-loaders that they so fear, we would have been wiped off the planet thousands of years ago. On the theoretical front, various game theoretical models, and even contests based on such models, have shown fairly consistently (AFAIK) that a tit-for-tat with first trust strategy is the most optimal.
As Joanna has pointed out, and as you point out above, in an environment of suspended paranoia it is difficult (for the general population) to see this existential point. Especially in a dominant epistemological framework where "I think" => "I am" follows that sequence.
IMHO,
--ravi