The vast majority of people can agree that fundamentalist religion is dangerous. It causes wars, murder, oppression, and all manner of atrocities. But what's wrong with just a little bit of god? Why is moderate religion so bad? Better yet, what about pseudo-religions that don't have gods? What's wrong with Unitarian Universalism? Why can't I believe in karma? Why attack my personal god? How does any of this hurt anyone?But the problem is more subtle than that. The biggest problem with fundamentalist religions are the beliefs. There's a problem with what the fundamentalist believes, and how those beliefs hurt people. So this is the focus, and people tend to miss the fact that there is really a second problem here, and this second problem is shared by even pseudo-religions. In fact, the problem is actually independent of what people believe. The problem is simply that they believe at all.
The problem is faith.
Now, we have to be careful here, because the word faith is thrown around a lot. Except in the world of symbolic logic and mathematics, it's nearly impossible to ever prove something with 100% certainty. The best we can do is show that something is probable. This is how science works. Science never proves anything 100% It just demonstrates that its theories are probably true. Now, if science doesn't give me 100% proof, why do I believe it? Some people say it's because I have faith in science. They are wrong.
Believing in something that is probably true does not require faith; it's just making the safe bet. If science can demonstrate that the odds of me being able to fly after jumping off a skyscraper are one in a trillion at best, then I'd better not jump off that sky scraper. This conclusion doesn't need faith, because it is backed by evidence. I have evidence that what I believe is probably true and that's why I believe it. This belief is not faith.
Then what is faith? As I will use it here, faith is holding a belief despite no evidence or even despite evidence to the contrary, and refusing to question this belief. At its best, faith says "I can't demonstrate that this is even probably true, but I'll believe it anyway." At its worst, faith says "I can demonstrate that this is probably not true, but I'll believe it anyway." Faith is reaching a conclusion that is not supported by evidence. Faith is reaching a conclusion despite the fact that no evidence can be given to support the conclusion's probable truth, much less its absolute truth.
So what's wrong with faith? There are really two problems, so I'll start with what I think is the easiest to understand. As I noted earlier, there is a problem with certain fundamentalist beliefs. The clear moral act is to call out such beliefs and let people know that they are problematic. Yet any moderate person of faith will have difficulty accomplishing this moral act. Here's why:
The fundamentalist believes something is moral, and this belief is based on faith. The moderate believes that same something is immoral, yet this belief is also based on faith. In order to defend the moderate position, which requires faith, the moderate is forced to make an unreasonable and thus weak attack on the fundamentalist's belief. The moderate must assert that while faith can lead to knowledge of morality, the fundamentalist got the wrong "knowledge" despite using the moderate's own proposed methodology. Because the fundamentalist and the moderate use the same method for deciding issues of morality, the moderate's attempts to discredit the fundamentalist are laughable at best. They amount to "you're wrong because I believe that you are wrong."
Just as bad is when the moderate refers to religious text to combat the fundamentalist. Religious texts are not only often self-contradictory, they are open to much interpretation, just like any other literary work. Claiming that some sacred text is the basis of morality will lead the moderate to once again make the ridiculous claim that the fundamentalist is reaching the wrong conclusions while following the right methodology.
To truly discredit the fundamentalist, one must attack the methodology of faith and of truth from scripture. Only by demonstrating logical, rational, and evidence-backed arguments for a different moral system can one build a truly strong case against the fundamentalist. But by supporting faith, the moderate supports the fundamentalist's methodology, and is thus unable to effectively attack the fundamentalist's conclusions. Furthermore, when the non-believer attacks the faith methodology of the fundamentalist, the moderate will often come to the fundamentalist's defense, because he will recognize that his own methodology is under attack. So not only do moderates fail to effectively argue against the fundamentalist, their support of faith actually undermines atheists' attempts to do the same. By condemning attacks on the faith methodology, the moderate is condemning the most effective way to combat fundamentalist thinking.
The second problem with faith is that it inhibits our ability to gain knowledge. This is most commonly seen in "< insert question here > isn't a scientific question" or similar claims. It is important to note here what is generally understood but not detailed in this claim. By "scientific", the claimant really means "scientific, mathematical, philosophical, or under the purview of any other reason/evidence/logic based methodology." What is really being claimed here is "< insert question here > is a matter of faith." That the only way to answer the question is by picking an answer and believing it. This leads back to problem one, in that by making this claim the moderate must necessarily claim that the fundamentalist has used the correct method despite somehow reaching an incorrect result. But the problem is even bigger, for faith does not actually allow for incorrect results. Faith cannot determine that one answer is better than another, and thus all answers are equal. By saying "< insert question here > is a matter of faith," the moderate is really saying that the question has no intellectually defensible answer.
This is a terrible epistemology. The faith based system ultimately answers all questions with "we cannot know... so just pick one and believe it." Faith gives us no knowledge, but it goes even further than that. By asserting that we cannot know, faith tells us that there's no point in asking the question. Not only does it fail to give us knowledge, it actually tells us that gaining knowledge is impossible. It discourages other methodologies that may actually decide on a single answer, and may allow us to determine why one answer is better than the others. Faith tells us to stop asking the question; to stop even thinking about the question. It tells us that there's no hope for a definitive answer and so we might as well give up.
Faith does not give you an answer. It merely stops you from asking the question.