Reason as memetic immune disorder by PhilGoetz

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this is: Reason as memetic immune disorder, published PhilGoetz on the effective altruism forum.
A prophet is without dishonor in his hometown
I'm reading the book "The Year of Living Biblically," by A.J. Jacobs. He tried to follow all of the commandments in the Bible (Old and New Testaments) for one year. He quickly found that
a lot of the rules in the Bible are impossible, illegal, or embarassing to follow nowadays; like wearing tassels, tying your money to yourself, stoning adulterers, not eating fruit from a tree less than 5 years old, and not touching anything that a menstruating woman has touched; and
this didn't seem to bother more than a handful of the one-third to one-half of Americans who claim the Bible is the word of God.
You may have noticed that people who convert to religion after the age of 20 or so are generally more zealous than people who grew up with the same religion. People who grow up with a religion learn how to cope with its more inconvenient parts by partitioning them off, rationalizing them away, or forgetting about them. Religious communities actually protect their members from religion in one sense - they develop an unspoken consensus on which parts of their religion members can legitimately ignore. New converts sometimes try to actually do what their religion tells them to do.
I remember many times growing up when missionaries described the crazy things their new converts in remote areas did on reading the Bible for the first time - they refused to be taught by female missionaries; they insisted on following Old Testament commandments; they decided that everyone in the village had to confess all of their sins against everyone else in the village; they prayed to God and assumed He would do what they asked; they believed the Christian God would cure their diseases. We would always laugh a little at the naivete of these new converts; I could barely hear the tiny voice in my head saying but they're just believing that the Bible means what it says...
How do we explain the blindness of people to a religion they grew up with?
Cultural immunity
Europe has lived with Christianity for nearly 2000 years. European culture has co-evolved with Christianity. Culturally, memetically, it's developed a tolerance for Christianity. These new Christian converts, in Uganda, Papua New Guinea, and other remote parts of the world, were being exposed to Christian memes for the first time, and had no immunity to them.
The history of religions sometimes resembles the history of viruses. Judaism and Islam were both highly virulent when they first broke out, driving the first generations of their people to conquer (Islam) or just slaughter (Judaism) everyone around them for the sin of not being them. They both grew more sedate over time. (Christianity was pacifist at the start, as it arose in a conquered people. When the Romans adopted it, it didn't make them any more militaristic than they already were.)
The mechanism isn't the same as for diseases, which can't be too virulent or they kill their hosts. Religions don't generally kill their hosts. I suspect that, over time, individual selection favors those who are less zealous. The point is that a culture develops antibodies for the particular religions it co-exists with - attitudes and practices that make them less virulent.
I have a theory that "radical Islam" is not native Islam, but Westernized Islam. Over half of 75 Muslim terrorists studied by Bergen & Pandey 2005 in the New York Times had gone to a Western college. (Only 9% had attended madrassas.) A very small percentage of all Muslims have received a Western college education. When someone lives all their life in a Muslim country, they're not likely to be hit with the urge to travel abroad and blow something up. But when someone from an Islamic nation goes to Europe ...