Religion is a Delusion/Mental Illness

[Dystopia]

No, there is a whole set of beliefs that are wrong.  One does not handle snakes or speak in tongues or even just attend church from the bare belief that there exists at least one god.

You are assuming that believing snakes can factually talk is part of mainstream Christian beliefs - Maybe for evangelists and bible literalists but from my experience all Catholic priests I've met (more than 10) reject literal interpretations and think talking snakes is a logical impossibility. I would agree that literally believing in talking snakes and other wishful nonsense would be very close to a mental diseases but that is not the case for most Christians who don't even read the bible or go to church that often.

Think how people would react to someone who had an invisible friend, who he claimed would magically protect him from poisonous snakes, and so he handled poisonous snakes in ways that do not prevent the snakes from biting, if it were not connected to Christianity.  Is that something a sane person would do?  

Since I like honest debate I'm going to tell you right away that you're making an overly gross simplistic definition with an appeal to ridicule in the mix.

Another problem is that it can be applied to just any ideology - Everything is a product of its historical, cultural and social context, so it's not productive to spend time wondering what Christianity wouldn't have been if X or Y didn't come into play.

Think about someone who ritually eats the body and blood of another man.  And who believes this to be of profound importance.  And imagine him actually believing it is really the body and blood that he is eating, that was magically transformed from bread and wine (see the Catholic doctrine of transubstantiation, which is official doctrine today).  Imagine how people would react, if that were not a part of mainstream religion.

Grand nonsense, even though there is no such thing as an official doctrine everyone must follow - You can be a Catholic because you are baptised and completely despise the church and the pope (it's what my mom used to do before deconverting). I completely get the part that some practises, miracles and rituals would be batshit crazy if it wasn't for religion and I'm not trying to be an apologist but those silly superstitions are not the definition of religion per se but rather some simple fundamental core beliefs that unite a group of people - In the case of Christianity it is the belief that you will go to heaven for following Jesus. I don't believe Jesus rose from the dead and I find that highly unlikely, but I don't think someone believing in it makes them crazy - Be aware that nurture and culture highly influence who you are - I would probably not be an atheist if I was, for example, black and poor (in my country).

The ONLY reason such people are not thought of as crazy is because they are a part of a huge group of people who have related beliefs and practices.  If there were only one Christian in the world (and to keep us from going to any extremes, let us say a mainstream Catholic who believes all official church doctrine), and if there were no history of millions of Christians, it is hard to see how anyone would not suppose the person was completely mad.

Again, this can be applied to any ideology - I'm thinking about some theories about the invisible hand and the free market - Does anyone think Adam Smith was mentally ill for believing it would work? - Are National-Socialists (nazis) mentally ill? They are bigots but they are not necessarily mentally retarded, being a racist or dumb does not make you ill.

By comparison, a person who believes the CIA is trying to read his mind and so he wears a tinfoil hat, is believing something less inherently ridiculous than mainstream religion.  At least the CIA actually exists, and they do try to find out what people are up to.

Religion is not merely one belief that is in error, it is thinking going terribly, terribly wrong.  One false belief does not create a religion.

Correct, but atheists make overwhelming assumptions about the number of beliefs and dogmas religious people have. Richard Dawkins and his fan club probably imagines most Christians as avid bible readers, everyday prayers who believe in most of the bible and go to church regularly or were severely indoctrinated. This is not reality, it is a fantasy irrational belief - Most Christians rarely step foot inside churches and don't read the bible that often and many don't even value the Old Testament aside from a few prophecies.. the only core belief is that you'll go to heaven if you believe and follow Jesus of Nazareth. Seriously, you don't even need to read the bible and you are no less Christian than literalists - Bible literalism in particular is very rare (unless it's in America) because Catholicism values academic education for priests and other church members and thus scientific knowledge and philosophy are important fields of study.

When you talk about believing in talking snakes you are talking about a specific denomination/church with specific beliefs, not Christianity as a whole. You can find liberal commie Christians and far-right fascist Christians. They can be as diverse as any other social group.

If I may ask, since you are proposing people being thought as crazy (I hope you are asking about the clinical definition) does this mean any irrational belief with strong repercussions can be considered a disease? Would racists be mentally ill? What about men who think women should be put back in their place? what about people who think aliens definitely exist or that jews rule the world?