A Mild Delusion
I sometimes hear from Christians that don't accept the ways of the fundies. Though we can both agree on their outrageous antics, we disagree when it comes to who takes the blame. That's where I put moderates in the same bucket as the fundamentalists. It doesn't matter what the amount of delusion is, it's the problems at the core that tie them all together.
Moderate and liberal believers act as a safe house for fundamentalists and provide a shield for them. Whenever the majority becomes comprised of relaxed moderates and anything bad happens that would cause them to think God is angry with them or the world or whatever, the moderates begin thinking, "What did we stop doing that would cause God to be vengeful? What changed?" They most often find the answer in fundamentalism.
If You Can't Beat 'em, Keep 'em Around
I used to be a fundamentalist Christian, growing ever increasingly moderate all the way out. Even though my tactics and reasoning were changing, I still had a mindset of a core fundamentalist. I'd see someone going "a little too far" on something, but I always knew their heart was in the right place. We had an elderly couple who began to grow more and more vocal over the choice of clothing the girls in the youth group wore to church: the dreaded and sinful pair of jeans. "That's no way for a woman to dress!" they could be overheard exclaiming as the congregation filed out of services. I didn't think God gave a damn about something as materialistic as pants, they backed up their objections with claims from the bible. I don't recall any particular passages, but it's not uncommon for a believer to say, "well, that's Bible!" when it comes to something they firmly believe -- whether or not it is actually stated in there. The point is that none of us less-sexist of the flock could shake the couple's certainty of the sin being committed, and we couldn't show them otherwise using the same "logical" tactics and arguments from the bible and faith. Those types of disagreements always come down to, "I'll have to pray about it".
The harboring of fundamentalist ideals is performed by all believers, be they liberal, moderate, or extremist. It's because the ideological framework is built using the same wood from the same tree (if you'll pardon the labored metaphor, and those that follow). The scaffolding may reach differing heights, but the foundation is the same unfounded illusion. Until the entire structure is torn down and can be rebuilt using actual knowledge and sound critical-thinking methods, the intellectual groundwork of moderates is indistinguishable from even the most delusional fundamentalists.