I found that the general purpose of any religion is to manipulate people. Those who actually believe it are just caught in that manipulation. Most modern systems are based on ancient principles, rules integrated into culture and passed down through generations. While this manipulation was originally necessary (and still is for stupid people), now it's mostly abused for profit or for the sake of the manipulation itself (people who do the latter are usually caught into it themselves, which happens when a person unable to understand the system gets elevated to a religious leader).
I hope that the day will come that the humanity would transcend the need for such silly things as religion and follow common sense, reason and science instead.
I've personally managed to achieve that by asking "And what if it wasn't exactly true?" and similar questions about most things I was told (it doesn't stop at religion either, I'm going to study high energy physics to be able to understand and, perhaps, challenge the most complicated, advanced and fundamental theories in physics), using strictly logical reasoning and Occam's Razor. There's no way to empirically prove any religion, world could function just fine without supernatural beings existing and there's a psychological theory explaining why people create and worship such beings.
Also, I couldn't say that God doesn't exist, but it is a purely psychological phenomenon instead of anything that has any direct influence in physical world. Sort of a collective delusion, created for the purpose of collective manipulation. When you take a closer look at it (from the psychological standpoint), religion is a fascinating phenomenon.
I was also amazed that I was unable to disprove Christianity by "direct" logical reasoning (something I attempted on every single religion lesson

), most things in it can be explained without introducing any contradictions, especially if you know something about the Bible in original. If it wasn't for Occam's Razor, there would be no reason Christianity couldn't be true.
Concluding, Christianity could be the most brilliant manipulation ever created by intelligent beings. I didn't analyze other religions in such detail, but I might do that someday.
I should also note that the above (any below) doesn't apply to far eastern religions, like Buddhism or Hinduism, but these are more about certain philosophies and ways of life than about worshiping deities. Perhaps even my "philosophy of doubt" is similar to one of the Buddhist philosophies.
Considering all this, I find fanaticism very stupid. It's religion for the sake of religion, not serving any actual purpose. Originally, it was meant to make people behave in certain way that was beneficial to the community as a whole. Rituals and mythology was just to make it believable. Now, people are obsessed with these rituals and mythology, ignoring the actual meaning. Fanaticism, of course, is beneficial to the church, since fanatics are easier to manipulate.