I may be wrong about this (which probably isn't a great way to start a blog), but one of the biggest fundamental misconceptions about agnostics and/or atheists, in my experience, is that they have chosen to believe there is no higher being as if they have/had no desire to believe in something beyond themselves or this world, and thus flippantly decided they must not need god. It's a misconception that my father, several relatives, and many of my friends hold without much thought.
And, while that may hold true for some, I find it very hard to believe it's true for anywhere near the majority of freethinkers. In fact, most people I've talked to have admitted that the desire to reach out for something beyond this realm is an almost innate thing to do; no doubt due to where, how, and by whom they were raised. But that just makes it all the more difficult to walk away from.
Personally, I was brought up in the heart of the US of A. The so-called "Bible Belt." A place where freedom of religion is nothing more than a fancy way of saying you can choose any breed or brand of Jesus you want... as long as you aren't too different from the rest of "us."
Because of this, I didn't even realize that there were people who didn't go to church every Sunday or that didn't believe in Jesus until late into elementary school (if any of my friends at the time weren't religious, they must have been taught to stay quiet and keep low profiles about it, because I can't think of a single one). And, as crazy as it may sound, for a long while I feared that I was the second-coming of Christ because of a Sunday school teacher who told us that even Jesus didn't know he was the son of god until he was baptized by John the Baptist.
Outside of a brief stint of rebelling against any/everything in middle school, I stayed on the "jesus path" up until college where a combination of good friends, great professors, and a respectful educational environment gave the the freedom to explore theology, philosophy, and my own life on open terms.
For me, the journey from aspiring Preacher to non-believer was just the beginning of a long, painful, tedious path that is still winding off into the unknown. It was not taken lightly, it was not a sudden thing, it was not an impulsive or reactionary decision; I wrestled with it for at least a solid year, fighting for the comfortable life that I knew and enjoyed with veracity. But... I just couldn't do it.
After a year of fighting, I called it quits and walked away from what I'd known my whole life and into the complete unknown.
This is where someone like my father would say something along the line of: "just choose to believe, take the leap of faith!" but it was out of my hands by then. I knew too much. I understood the bad theology taught as truth by the church, I knew the context of the Bible, I had experienced the bureaucratic nature of church polity, and I hated the consequences that come from blind faith (not to mention, there is no logical reason or proof to justify a belief in God).
As the Gnarls Barkley song goes, "...it wasn't because I didn't know enough, I just knew too much," and it really did make me feel crazy.
I felt, and was, overwhelmingly alone. I was attending a private, baptist affiliated college which maintains strong religious ties to this day. Of my class, I would guess that at least eighty percent believed in god on some level or another. I have never felt as alone and empty as I did that first year of quiet disbelief. And I doubt there was a day that went by where I didn't second-guess myself or hope for amnesia to wipe the slate clean so I could go back to the simpler life I remembered.
Thanks to staying in this general area, everywhere I've worked and lived has been filled with people who assume that if you're nice and "normal" then you must believe the same as them; a place where, if you speak up and, thus, break their bubble, your relationship with them drastically changes forever. Even at my current job/school/etc, I don't feel comfortable or "allowed" to come out and speak my opinion in the open; those around me would rather be ignorant to what I think and believe than know for sure that it conflicts with their views. They would rather never get to know me, than realize that we are different.
I say all of that to hopefully illustrate a very simple point: this was and is not taken lightly.
In my case, it took years of doubt and research accompanied by a lot of fear and finally some well-founded courage. It was one of the hardest choices I've ever made and will probably ever have to make, and it still, and will always, impact my life and relationships with others... whereas the process of belief was taught to me from day one; it took no thought, required no real faith, and was never my choice.
Maybe that is why many agnostics and atheists turn militant when their beliefs and choices are approached as nothing more than childish rebellion. Although it's not right, it is understandable; because, in all likelihood, they are just returning the same childish behavior and ignorance that they feel continually assaulted with.