Religious faith is not a delusional disorder in the same way that strawberries are not a delusional disorder. It does not meet the criteria. Delusions are a very specific set of symptoms, indicative of a psychosis. Postulating a divine creator, or any form of philosophical thinking, does not indicate delusional symptoms. And particularly delusional disorder, which is an atypical and uncommon condition. In order to make the correlation you have, you would have to assume that the religious person is experiencing hallucinations. Now obviously, this is not the case for most people, regardless of their religious affiliations. Hallucinations, visual or auditory, would rule out delusional disorder since the condition itself does not require a person to be psychotic. Such a diagnosis would be made via process of elimination. I don't see how you got from what you falsely believe to be a psychotic symptom to delusional disorder, without first taking into consideration any other psychotic symptoms the patient may be exhibiting. Most people on this planet are either religious or spiritual. Delusional disorder accounts for a tiny percentage of first admissions.
My answer to that rebuttal: I agree with your assessment if one looks at it from a clinical point of view. “Postulating a divine creator or any form of philosophical thinking” is not a symptom but believing it, as a certainty, is. There are many levels of delusion and only when that delusion become extreme, it will be clinically accepted it and treated. A slight cold is not the flu.
Delusion starts with indoctrination, mostly in childhood, and the type of indoctrination highly depend on the culture and environment you were brought up in. Take the simple case of belief in Santa Claus, “He sees you when your sleeping, he knows when you awake, he knows when you are bad or good, so be good for goodness sake”. This parody on the Christian god, historically invented to control behavior, based on the actual mixture of several cultures is an example of a delusion believed by many children. (love to further in detail on this but not here at this time). This doesn’t qualify in your terms as a clinical delusion, but it is in fact a delusion, it is real for the child. This delusion, if not interfered with, will eventually be resolved at about 6 to 7 years of age, according to some studies, because the child starts questioning such thing as flying reindeer and bringing gifts to every child in one day, so they shed their delusional beliefs. A person who cannot do that and keeps believing in Santa would indeed suffer from a clinical case of DD. The parallel with religious beliefs is astonishing.
Many religious indoctrinated children, including myself, start questioning the delusional dogma of religion and grow out of it. Many “fence sitters” are also questioning the validity of the delusion but the stigma of being an unbeliever is still very evident and can be a negative influence in your position in society and even family and friends. Then there are multi levels of delusion, from feeling assured that a god must exist and don’t understand that there are people who cannot accept that, to extreme case such as people who will murder others (an abortion doctor, for example) and are a danger to society. Christianity does not burn witches any more and is relatively benign, compared to Islamic extremists, but still is delusional. This all points to an instinct we inherited because it was useful in the maintenance of the tribe but is now creating havoc in the world were we essentially have become one tribe.
You stated “most people on this planet are either religiously or spiritual” true, however the existence of a spirit or soul is also a man-made delusion, which can be traced back in antiquity. If you are interested, go to my Blog on “The origin of the spirit”, I can’t write a book here. The spirit which enters the baby on it’s first breath and leaves the body on it’s last breath to rejoin the Great Spirit (the atmosphere) has mistakenly become a delusional entity (“Spiritus” is Latin for Breath). The word “Spiritual” has no real meaning.
Hallucinations, visual and auditory experience are indeed not symptoms of DD but when one believes that they are real manifestations of a Deity, it is. The recent case of a judge who interfered in a jury’s deliberation because god told him the accused was not guilty, is a prime example of DD. The only reasonableconclusion is that Religion is indeed delusional, “the holding of beliefs or impressions that are contradicted by reality or rational argument”.