Religion is a Delusion/Mental Illness

[Angrboda]

Bullshit.  This is a hasty generalization.  Simply because some mental illness diagnoses may be the product of cultural prejudices does not justify the conclusion that they all are, nor its corollary that religion would be classified as a mental illness if it weren't socially acceptable.  People believe all sorts of weird things, from alien abduction to contrails, without that belief rising to the category of mental illness.

Whether a particular mental process, or set of processes, are labeled "mental illness" or not is a function of attitude towards those thought processes.  It is not like finding a virus and saying, aha, there is the problem!  It is that some thoughts, or sets of thoughts, are judged to be sufficiently different from what is judged to be good that they are given that particular label.  It is a value judgement about a state of affairs, not an objective analysis of the state of affairs.

With all due respect, I don't think you know what you're talking about. Name three diagnoses that fit the pattern you are claiming.