For example, some dudes say that it's self-evident that all men are created equal. Then somebody notices that this doesn't really jive with the whole slavery thing. So at least some of what gets called moral progress is just people learning to live up to their own stated principles.

By this reasoning, abolishing slavery was moral progress, but declaring that all men are equal was moral regress.

If the fallacy is slavery, then moral progress. What if the fallacy is that all men are created equal?

By your measure, hypocritical values dissonance, we morally regressed when some dudes said it was self-evident that all men are created equal, and have indeed been morally regressing ever since, since affirmative action and so forth are accompanied by ever greater levels of hypocrisy and pretense. While the abolition of slavery reduced one form of hypocritical values dissonance, other forms of hypocritical values dissonance have been increasing.

Example: Female emancipation, high accreditation rates for females. Most successful long lived marriages are quietly eighteenth century in private, and most people, whether out of sexism or realism, quietly act as if female credentials are less meaningful than equivalent male credentials. Your criterion is neutral as to whether we do this out of sexism or realism. Either way, by your criterion, it is an equally bad thing, and there is a mighty lot of it going on.