I think that it would be fair to say that in the United States of America athiests are discriminated against more than christians are. Americans are guaranteed freedom OF religion, but not freedom FROM religion, for example.
This is certainly debatable. I won't try to establish a counter-argument or anything here; I just want to point out that someone who is not religious would find the above statement true, and a traditionally religious Christian/Muslim/Jew is much more likely to disagree and believe that adherents of traditional religion suffer more discrimination. It's hard to measure such a thing! Examples abound on both sides.
It is hard to draw the line between delusion and religious beliefs. E.g., 'I'm literally drinking the blood of Jesus' (catholic doctrine of transubstantiation etc). It can be similarly hard to draw the line between delusion and scientific beliefs. E.g., 'I believe the future will be like the past even though I have no evidence for that'. 'I believe that there is an external world that roughly matches the way things appear to me - even though I have no evidence for that'. Try believing the converse (that the world will end tonight, or that there isn't an external world) and you will be considered delusional, however.
I think you focus too much on the fact that delusions are false (which they are) and without corroborating evidence. There's a lot more to it: delusions are meaningfully psychopathological -- they are symptoms that reflect and point us to illness. Dogmatic is different -- healthy people throughout history have believed in things such as "the future will be like the past" or "the Bible is the inspired Word or God" or "my place in my next life will be determined by my conduct in previous lives."
Sims, in Symptoms of the Mind (I love this book by the way), gives some criteria distinguishing religious belief and delusion. They seem to me to be, beyond interesting, very useful.
Religious belief tends to be
1. Metaphorical/spiritual. I might believe "Christ lives in me," but I don't believe that some dude is actually in my body somewhere. Schizophrenic patients tend to have concrete and over-inclusive thinking, not fine spiritual distinctions.
2. Freeing. A religious person usually sees their belief as making them "more free," "better able to do what one wants to do." This is very different from the first-rank delusions in Schizophrenia which are often delusions of passivity.
3. Religious experience provides and sustains meaningful activity. Religious people, based upon beliefs, go and write books, build synagogues, preach in a coherent way that attracts others. Patients with delusions often have difficulty initiating and maintaining even everyday goal-directed activity.
4. Unlike with delusions, in religious belief there is a preservation of ego integrity. The believer also follows a source of religious authority, not delusional evidence. If I believe the Koran is dictated by God, so I believe stuff in it ... that makes sense. If I believe I am the true heir to the throne of the United Kingdom because my neighbor commented on my tattoos ... that's delusional percept.
5. Religious beliefs are held alongside doubts. Even very devout Muslims/Buddhists/Catholics/etc can (almost always) say to themselves, "I believe these things, but I can imagine things being different." But for a delusional person, you might as well ask them to question the existence of the chair they are sitting on.
Delusional patients, additionally,
1. Often have other symptoms of psychopathology: hallucinations, thought disorder, mood disorder, etc.
2. Show a lifestyle, behavior, etc. that are consistent more with the natural history of mental disorder as opposed to a personally enriching life experience.
Conclusion: there is a difference between delusion and religious belief. And it's NOT about content or culture/subculture ... delusions can be religious, and religious beliefs obviously can be false. It's the about the form of the belief ... the cognitive and perceptive changes that lead to the formation of the belief -- why and how that belief is held.
If we confuse delusion and religious belief based upon a general feeling of suspiciousness towards religion, we are doing a huge disservice to our patients! The religious beliefs of the treater should be irrelevant here ...