I am a Christian, but not much of a church-goer. I feel that I see through the misinformation and lies. And, you feel the same way, even though your belief is the polar opposite of mine.
Perhaps it is human nature to think that our own personal belief system is the "truth" and that others are just plain deceived by believing anything different than our own beliefs.
I once heard a 'theory' about the evolution of the male/female counterparts (ie, how entities became male and female by the process of evolution), and it was the most hysterical story I had ever heard. I laughed for 10 minutes because it was such fanciful myth and required much more *faith* from this "scientist" than my God requires of me. And, at that time, I wondered (like you perhaps), "how are people so deceived".
But to answer your question, which is, "how are people, like myself, so deceived, and why can't I see behind the lies of religion":
Generally, I would say I do see behind the lies of religion, and I don't view Christianity as a religion. "Religion" to me, is the tradition, the robes, the gothic buildings, the unquestioned hierarchy of leadership, etc. But, "Christianity", to me, is just a simple belief system, or an "agreement system".
And, I simply don't see the relationship between food and religion. You seemed to imply that if a person begins to see that eating eggs, milk and fish are not healthy, he or she should also see the "truth" that there is no God. Where do you see the parallel?
On another note, I have seen quite a few comments on some 811 / fruit / vegan websites that lead me to believe that most vegans are pagans or new-agers. It seems to me that it is often a belief system, and generally a pagan or new age belief system, that motivates vegans to eat fruit and veggies. For example, on one popular, well-known site, one of the owners expresses her belief in Gaya. This can be frustrating for people like me who simply want to know what is best for their bodies. I don't want to be taught to eat a certain way because it's a "sin against Gaya" to eat any other way.
And then there are some who preach the Vegan lifestyle not from religion, but simply because they don't like to hurt animals. I agree with this emotionally, but I prefer not to use my emotions to reach a conclusion about health. Perhaps somewhere there is a group of people who don't want to hurt animals OR PLANTS, and all they have left for food are the rays of the sun. I doubt that kind of "diet" would last long, but I'm sure there are a few misguided, emotionally convinced individuals who attempt such a "way of eating".
You mention that eggs are bad for us - why? And fish? Really? For everything you can say against fish, there are 10 other people who can derail 811 (including 811's cousins in the raw food movement, vegetarians and the low carb and paleo people). One 90 year old gentlemen, who is in excellent health and sharp as a tack, writes extensively on his website about the dangers of a 100% diet (especially a high fruit diet). He has concluded with his research that a 100% vegetarian diet is great in one generation, but as the individuals give birth to successive generations, and each generation is 100% vegetarian, problems arise.
For me personally, I find that the 811 way of eating feels best for my body - especially in terms of digestion and bowel movements. For 15 years or more I had IBS, and eating Paleo style cured that. But I was constipated all the time. 811 cures the constipation for me. So, I am seeking health - not Gaya, atheism, a god, my own Christian God, or any other entity - for me, this is about food and health and body - not about religion.
I hope that answers your question, or gives you some insight into the inner-workings of the mind of a believer. But you may have been referring to other member's new-age beliefs (in contrast to my christian beliefs), and unfortunately, I can't speak for them.
And now that I have written so much, I'll ask my own question:
Why is it so important to you to convince people not to believe?