During my wavering Christian years I started to hit the arguments and rebuttals for the existence of God. There are plenty of books on the topic.
I started with Aquinas and was fairly surprised to see how easily his arguments are dismantled.
George Smith's The Case Against God went through all the arguments with sound rebuttals. It was an eye opener for me. Why did I believe in God? What reasons did I have and how could I defend them?
I read with the intent of finding the rebuttals to atheist claims. What I found was that arguments for belief in god(s) fall into certain categories. The problems come when you argue against someone who won't define any concept of god. It boils down to the idea that a vague non defined "thing" isn't worth worrying about let alone worshiping or acknowledging. Plus, the burden is on that person to explain the origin and other claims he makes about his undefined "thing" god. There is no reason to make up a layer of undefined mystery to explain anything. It only adds more questions.
So what reason did I still have to believe in God once I saw that the arguments were not there? I personally didn't need to rationalize any more to make up reasons to believe. I could not defend my position any longer so my views changed.
However there are still a couple reasons I think are valid for people to use to defend their belief in God. If someone believes for comfort reasons, I can understand why. Life is hard enough. If a God gets them through life then that's their coping tool. As long as they don't need to project their beliefs onto others (through laws or proselytizing) to validate their belief it's not my problem.
Another reason I think justifies a belief in god is for the people who have no control unless they think they are going to be watched or rewarded. If belief is the only thing that is keeping a person from killing, raping and pillaging, then I say let them go to church 24/7. These people are not to be trusted if they should lose their faith.
Of course in schools we do not (usually) address the logic problems - the arguments for and against god with rebuttals- unless it is an university philosophy class. I think it is unfortunate that religion receives protection from scrutiny because it is "sacred" and people get so defensive when their beliefs are scrutinized.
Is there a god? I have no idea. I cannot argue effectively for the existence of one so by default I lack belief. I CAN usually argue effectively against any definitions people often assign to their god (such as benevolence, omnipresence, etc.).
Another problem is generally that standards for evidence are very low for believers and they are not concerned about evidence that does not fit their views. There is no point discussing arguments with believers who don't use logic, evidence or who won't define anything. Once they have decided based on emotion and have a preconceived conclusion, reason is impotent.
Sometimes people seem to think that the belief in god defaults to the belief in Jesus, the Bible, and all the dogma that follows (anti-gay, creationism, etc)
I'm basically an agnostic atheist, I think "God" could exist but I sure as hell don't believe in "the Bible." Just because you believe in God doesn't mean you have to believe in the fables of some ancient middle eastern people and all its accompanying dogma, mythical stories, commandments, salvation methods, and so forth.
I have absolutely no qualms about people who believe in God. I just don't like it when believers judge and persecute others for not believing exactly as they do. "Sorry, Ex-CultMember but unless you accept Jesus as your personal lord and savior, you're going to burn in everlasting hell with the devil." or "THE BIBLE says homosexuality is a sin, therefore we can't tolerate gays or allow them to be married."
Just because YOU believe in some particular religious book doesn't mean the rest of humanity (atheists or believers) has to.
I do not believe in God, but I also believe that it has not been proven that that God does not exist. In other words, I do not know for absolute certain that there is no god, but based on the evidence I have seen, I believe there is no God.
That said, I also must point out that the above statements do not mean I think that there is any realistic chance that there is a "god" in any supernatural sense. I, personally, think that there is no reasonable chance that there is a god. Yeah, there are those that say "Well then, it is possible there is a God, so I'm going to believe in God". It is also possible that someone could win the California Lottery 75 times in a row, but that does not mean it is sane to believe it is going to happen.
That said, I think the link posted in the OP does a good job of dealing with the concept of God and goes way beyond the Christian concept of god.
"I contend that we are both atheists. I just believe in one fewer god than you do. When you understand why you dismiss all the other possible gods, you will understand why I dismiss yours." - Stephen F. Roberts