My Cognitive Theory of Politics is catching on a little bit.
We need not concern ourselves with the lengthy exchanges between Harris and Haidt on this matter. The underlying difference between the two of them comes down to the central dichotomy in Arthur Herman’s The Cave and the Light. Harris is a rationalist trying to derive truth through pure reason. Haidt, meanwhile, is an empiricist simply describing things as they can be observed.
In other words, Harris is subscribing to the unconstrained Utopian vision. Implicitly he imagines a world where human beings are no longer groupish or tribal, and the social functions traditionally provided for by religious institutions are no longer needed.
Even thought he is an atheist himself Haidt sees no such possibility and it seems to me the weight of evidence is entirely on his side.