The issue that got Sam Harris into so much trouble was his assertion that decent, reasonable moderates were as much a part of the problem as the crazed religious zealots.
I think he's right. And I just read a fascinating passage in Stephen Pinker's The Better Angels of our Nature that helps explain why.
Pinker is discussing the Prisoner's Dilemma, and how the simple strategy Tit-for-Tat is generally the best algorithm for repeated iterations. You start out cooperating, and then you just do whatever other guy did last time. This not only accords with our natural moral senses, but it's also mathematically optimal (which of course is not a coincidence).
Not only does it work best for the individual, but it works for the community; over time, the Cheaters are weeded out, and soon you have nothing but rational players.
But, here's the thing. Suppose there are a group of Samaritans in with your population. They always cooperate, no matter what. Sounds noble, right? And for the Tit-for-Taters, it's fine; they'll always cooperate back. Everything's great.
Except it isn't. The presence of the Samaritans keeps the Cheaters alive. Because there is a population for the Cheaters to exploit, they stay in the game, cheating everyone else and forcing them to cheat, and in general ruining it for everyone.
Yes, the Cheaters are the bad guys; but the system would purge itself of them if it weren't for the Samaritans.
And this is (mathematically) how nice, reasonable, perfectly decent, respectable, admirable, honorable people... contribute to religious zealotry.
It's a little bit like how a perfectly decent pothead's habit contributes to South American police states. Or the weekend wine drinker makes alcoholism possible. At some point you have to draw a balance between your private indulgences and social harm. Frankly, I don't have a problem with weekend drinkers or potheads (the harm they cause should be solved by other means, like regulation and legalization). And I'd like to not have a problem with nice, moderate religious types... but religion has caused so much harm that I can't. Alcohol destroys lives; religion destroys societies.
Maybe I'm wrong. Maybe once we get the fire under control, weekend mysticism will be fine. Maybe I'm over-reacting. I dunno; all I have is my hunches and prejudices.
And, oh ya, math.