Religion is a belief. You can't rationalise a belief -- that's why being religious is a personal experience (though one you can experience when in the company of others, certainly). If you want to have a religion -- by all means, go ahead.
But when you maintain that your religion is always right, and therefore that anything which criticizes your beliefs must be wrong, then things start to go astray. That is the post-rationalist mindset, and it is rampant these days -- verily, a throwback to the Dark Ages.
The freethinkers are right: religion is used to assert control over the general population. In the name of religion, you can get people to do all sorts of crazy things. I hear people maintain that islam is a religion of peace -- and it might very well be, but what about the crazy fuckers who blow themselves up in a bus in the name of the islam?
The thing is, that most religious activism does not serve a religious purpose. Blowing yourself up at a wedding does not convert people to your religion, nor will it make people lead Good Lives (as defined by your religion). Campaigning against same-sex marriages will not suddenly make devout zealots out of people who were not under your banner already. Your personal religious experience will not improve if you undertake these things.
Instead, these actions serve a political agenda. An agenda that is set by clerics who crave power. Clerics who abuse the trust other people placed in them, who abuse the words of their chosen holy texts to manipulate others to do their bidding, who maintain that this is all the will of their chosen deity.
I know some pretty strong words, but I have no words that can describe how much I despise 'people' like that -- nor what manner of misery and painful death I wish upon them.
Of course, if your religious sect is the base of your power, you can not allow anything to challenge the beliefs of your flock. If they start to doubt you, your influence wanes. Obviously, you need to manipulate the thoughts of your flock so that they will instinctly reject anything that contradicts your ideas. In fact, such things might even serve to energise your flock: whip them up in a frenzy over a real or imagined sleight against your religion! This will serve to make them bond much stronger to your clique, so that it is even easier to get them to do all sorts of crazy stuff to further your own political agenda!
Think of this when you see muslims burning Danish flags. Think of this when you see pro-life protesters. Think of this when you see bans on stem cell research. Think of this when you see school boards being pressured into teaching intelligent design.
"That's why those who have an unquestioning faith in the correctness of the moral teachings of their religion are a problem: If they haven't conscientiously considered, on their own, whether their pastors or priests or rabbis or imams are worthy of such delegated authority over their lives, then they are taking a personally immoral stand.
That is perhaps the most shocking implication of my inquiry into the role religion plays in our lives, and I do not shrink from it, even though it may offend many who think of themselves as deeply moral. It is commonly supposed that it is entirely exemplary to adopt the moral teachings of one's own religion without question because — to put it simply — it is the word of God (as interpreted, always, by the specialists to whom one has delegated authority). I am urging, on the contrary, that anybody who professes that a particular point of moral conviction is not discussable, not debatable, not negotiable, simply because it is the word of God, or because the Bible says so, or because "that is what all Muslims (Hindus, Sikhs...) believe, and I am a Muslim (Hindu, Sikh...)" should be seen to be making it impossible for the rest of us to take their views seriously, excusing themselves from the moral conversation, inadvertently acknowledging that their own views are not conscientiously maintained and deserve no further hearing."
-- Daniel Dennett in an article for the Chronicle of Higher Education, which is sadly placed behind a registration.