First of all, while re-reading some of my posts I noticed that my ideas are quite rapidly evolving - absolutely a good thing, but it does look funny on such a polemical blog where I viciously argue why I'm right and then immediately alter my position. For example, I said in 'The Trials of Atheism' that I disliked the term "atheist" because it implied such certainty - that there WAS no divine. "Agnostic" seems better because it admits you can't know either way.
But I've changed my mind on that one, and here's why: since there is no evidence for a supernatural, to be religious requires actively augmenting your understanding of the world with faith. Atheism is the default position - it requires no leap of faith and thus is the legitimate position (I'll get to why faith does not constitute legitimacy - that's what the article proper is about). To put it another way: agnosticism is the victim of the golden mean fallacy, claiming that both theism and atheism are of equal validity and thus we should mediate between them. But atheism does not insist that there is no god - instead, gods are not among the things that atheists believe exists. They simply haven't augmented their worldview with unsubstantiated faith.
This leads very neatly into the main point I wanted to make - that faith is not a virtue; it is instead one of the most significant, and thus dangerous, fallacies that we humans can make. Faith is not simply limited to religion, though - in fact, faith is what makes religion the blight that it is. I would say that I have no problem with religion itself, but faith and religion are so inextricably bound up that they are essentially one and the same.
It's important to make a distinction here: between faith and belief. Whenever one criticises faith, it is retorted that everything is based on belief regardless of your religiosity, and that to criticise theists is to ignore your own unsubstantiated position. Here, faith and belief are taken to be interchangeable (which theologians, in an absolute master-stroke the likes of which have never been repeated, have convinced us all are a beautiful expression of spirituality). But they are not interchangeable and are instead quite distinct.
To believe in something is to think it true, based on available and skeptically-examined data - when the data changes, your belief changes with it. A belief doesn't have to be correct, it simply has to have evidence supporting it (even if this is "scientists have found that..." - skepticism allows you to reasonably believe what a scientist says, even though being a scientist does not automatically make someone right).
To have faith in something is to think it true, because you think it's true. It really is the ultimate in existential arrogance - to claim the existence or non-existence of something based solely on whether you deem it to be so. Faith can change, obviously, but here the motivation is one's own whims rather than external evidence. Godwin alert: Faith is just as much about claiming that the Jews are a threat to the Aryan master race as it is about religion. If it's unsupported by evidence and motivated by subjective forces rather than external ones, it's faith.
Consider: you see a ball being put in a box. Or hell, someone tells you there's a ball in the box. You now believe that there is a ball in the box. You don't have to be right, but you still have sufficient reason to believe that. On the other hand, if you simply see a box and decide there is a ball in it - that is faith. You've no reason to believe it other than what you have yourself decided. One of those is a legitimate worldview and the other is not. Here's why:
Faith, as the ultimate in subjectivity, requires no justification. It is a strongly held belief that receives no verification and no constraints, and thus is license to declare whatever you want to be true. Encouraging people to believe, and thus do, whatever they want is diametrically opposed to society; faith is the antithesis of civilisation. We have laws which we apply to everyone, because we acknowledge an objective reality in which we all interact. We (ought to) have leaders who aim to have the best understanding of reality, so that they can make the best possible decisions. Faith denies all of that.
Yet it is trumpeted loudly as the greatest virtue, theologically speaking. Those without it, let alone those who deny it, are lacking spiritually and apparently lead deeply unfulfilling lives. As I said before, this is the master-stroke of theology - to take the weakest aspect of religion (ie. it being wrong) and making that its selling point, THEN to attack those who call bullshit. It's like stoning to death the kid who pointed out that the emperor wasn't wearing any clothes.
Moderate theists (I refrain from saying "believers" given my earlier distinction) will often claim that it's wrong to point to all the extreme examples of religion since there are so many loving, peaceful religious people who properly understand God's message. Faith, for them, is not about violence and subjugation, but rather kindness, joy and inner peace. Their's is the "right kind" of faith. Except... when you attempt to give faith any kind of legitimacy, you give ALL faithful legitimacy. If you say that whatever you believe is right, then suicide bombing or honour killings or even goddamn genocide are all right. The moderate who justifies their religiously conservative lifestyle with faith is ultimately no different to the extremist who justifies mass murder with faith. The moderate certainly gets no moral high ground over the extremists - any promotion of faith enables extremism and self-justifying violence.
The second reason faith is such a detriment to society is the necessary compartmentalisation that goes on in the minds of the faithful. Because it is not possible to maintain completely rational, skeptical thought AND maintain faith, the faithful must suspend the former to preserve the latter. This opens them up to all kinds of manipulation because if something is presented under the guise of faith then it will slip past that person's rationality. This is how we get perfectly normal, loving people who vehemently oppose gay marriage. It's how people throw their money at blatant religious scams or join dangerously insane cults. It's how we get WWII, the Cold War and all its proxies, all the genocides of the past century and the Age of Terror in which we now live.
It's, ah... it's not so good.
TL;DR - Faith is promoted as a wonderful thing in today's society, when it can only ever be an enabler for extremism, violence and manipulation. If you want to make a good person do bad things, use faith. Suspend their rationality - tell them that it diminishes them as a person - and they are at your command.