When is a Religious Belief Delusional?

[Angrboda]

Well then, are you differentiating between the theist simply being wrong and being delusional?

Nope, I'm saying they are both. The same as people who believe in aliens, ghosts or witch craft. They don't necessarily meet the clinical definition either yet are wrong and delusional. 

That doesn't really answer the question. They can be both and both are the same, or they can be both and yet being delusional entails something more than simply being wrong. If it's the latter, then what is that something more that makes a person delusional? If not, why use a term that is perceived as insulting when there is a non-insulting synonym?