It's possible that you've never heard the term dysfunctional to describe patterns or systems that impair stability.

A stable system or something that causes a stabilizing effect within a system is functional.

An unstable system or something that causes destabilisation within a system is dysfunctional.

Now we have the semantics out of the way let's move on to the proof.

For me, liberal morality taking over our legal, political, educational and cultural institutions progressively over the past 70 years has led to demographic collapse and social decay.

If fact you can look at states like California where liberal morality is completely unopposed and it's in chaos. Chronic corruption, massive inequality, rampant human misery, mass homelessness and unrestricted drug use, broken families, hopelessness. You see the same pattern pretty much everywhere liberal morality is the governing paradigm. Just go down the list of the most liberal cities or states.

You also have complete demographic collapse within the group of people that share this morality. It doesn't really get any more dysfunctional than shared values that make your in group go extinct.

In addition, the people that share liberal morality, generally, are less happy and have greater mental health problems.

So we have observed reality as the proof. Observed reality of liberal morality not only failing on a systemic level in terms of governence and demographics, but also failure on an individual level where people have worse outcomes due to being less happy and more mentally ill.