How is causality relevant? The absence of continuous general increase is enough to falsify the Whig-history hypothesis, given that the Whig-history hypothesis is nothing more than the hypothesis of continuous general increase -- unless we add to the hypothesis the possibility of 'counterrevolutionary' periods where immoral, anti-Whig groups take power and immorality increases, but expressing concern over things like illegitimacy rates, knockout games, and inner-city dysfunction is an outgroup marker for Whigs.
You need evidence actual decline to justify reaction. Othewise, why reverse random drift?
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.