Where I disagree with Gibb is that post-liberal (integral) stages “can distinguish those policies which are healthy for each level and those which are unhealthy and decide what is best for the whole social system.” I discussed this in the thread “ladder, climber, view.” This is Wilber's terms for how we differentiate transitional from enduring structures; the former are transcended and replaced while the latter are transcended and included. Moral views are transitional structures so previous moral levels, healthy or otherwise, are not included. And this aspect is not addressed by Gibb's limited SDI model.
"The Graves/Beck system does not clearly distinguish between transitional and enduring structures, nor between basic and self-related structures. In my own system, the basic structures are enduring and remain fully active capacities available at all later stages, but most of the self-related streams (such as morals, values, and self-identity) consist of transitional stages which tend to be replaced by subsequent stages."