When is a Religious Belief Delusional?

[Neo-Scholastic]

Is belief in the existential equality of all human beings delusional? No natural facts support that belief.

Not if it's taken to be a political construct rather than an inherent or objective fact.  Moreover, even as an inherent or objective fact, it can be derived from the morals of fairness, that all should be treated as equal, regardless of any objective existence of such an equality.

Any notion of fairness already presupposes some measure existential equality. You're arguing in circles. Let's step further back. I believe there are moral facts. Are those delusions?