Not sure I buy the Sam Harris argument that moderates are sheltering the extremists. Especially with Christian religion, the cult think by design, yields even stronger passions when your tiny little group is the only god-fearing bunch on the planet. The extremists already typically denigrate the vast majority of “luke warm” Christianity and are skeptical that most Christians are really Christians, so they have many reasons to completely disregard whatever the compromised moderates and liberals think.
I don’t think it’s worth saving the argument (since as you point out, moderates cause immediate problems with solidarity in their own right), but you might be able to say that more people are exposed to religious thinking that tends towards extremism, by being a moderate. The God of the static Bible certainly is no moderate, so there will always be a turn over.
So what do you all think? Can the argument be saved after all?