Religious moderatism empowers religious fundamentalism by affirming the false premises that religious fundamentalists rely on.

In order to argue against a religious fundamentalist in an atheistic society, all you have to do is point out that the religion, itself is false -- and then they have the burden of proof to demonstrate the contrary. AKA, the anti-fundamentalism side gets the high ground.

In order to argue against a religious fundamentalist in a religiously moderate society, you have to sorta walk the fine line of affirming that the religion in question is true while arguing that the fundamentalist doctrine is untrue. In that case, you're on even footing, arguing interpretations of the same text, which really sucks since religious interpretations are subjective by nature.