I have gotten this question so many times, I don't think I can overstate it. "Why are you so angry with 'God'?" "What do you have against 'The Lord,' your god?" "What is your problem with 'God'?" If I had a problem with someone who doesn't even exist, I don't think I'd be in my right mind anyway. Though if you want to define "God" as the idea of a supreme being rather than the being itself, then that is something I have a problem with.
Well, far more than just a problem... The very idea of a supreme being is entirely misguided on every foundational aspect of it. It is not enough to say that creationists have provided me with no reason to believe it, but that they've even provided quite an abundance of reasons not to believe it. Not only have they shown without exception that everything on which they base their belief is shallow at best and most often fundamentally untrue or unprovable, but that the very same belief leads down paths which are demonstrably harmful, and without merit.
I know a great number of people would like to point to all the wars and killing caused by religious conflicts (something that all religious people will try to argue back against by associating any murderous act performed by atheists to be specifically caused by atheism without demonstrating this chain of causality)... but to me, this is not the most serious issue. Partly because, even in an all-atheist world, we'll still have wars over resources and people who want power by illicit means. Sure, we can also point out that ALL statistics of ALL developed nations show that a higher relative percentage of atheists within a reasonably large population is accompanied by lower rates of crime, lower rates of drug abuse, lower suicide rates, lower murder rates, lower teen pregnancy, lower divorce rates, lower obesity, lower school dropout rates, higher literacy rates, higher longevity, and probably a whole bunch of others I can't entirely recall off the top of my head. Still, that's not really what I consider the most serious issue of all because they're effects rather than causes.
No... to me, the biggest problem with the idea of God is that it allows just about anything to be a virtue or a vice. It is completely without morality because it redefines good and evil in terms of obedient and disobedient. It is entirely without thought and without remorse in anything. The common virtue to all religions (parody religions like Pastafarianism notwithstanding) that has no place being considered a virtue is gullibility.
Yes, you read that correctly. All religions consider gullibility a virtue. All of them want you to be mindless saps who will swallow anything they feed you, so long as you only take what they feed you and nothing anybody else tries to. Yes, they try to wrap it up in flowery language and call it "faith", but all it really is is being an idiot, plain and simple.
Do I have a problem with all the religiously-motivated violence? All the religiously-guided anti-education movements? All the stupid pointless rituals people do in the name of religious tradition? All the kids negligently killed by their parents who seek the advice of ancient holy wisdom in lieu of real medical science? All the condemnation of independent thought? All the outright misogyny and xenophobia intrinsically promoted by religions? All the association of religion where it doesn't belong even if it had some truth to it? All the ways in which religious belief serves as a barrier against reality? All the ways in which religious language gets used to terrorize children into blind obedience? All the deference to the notion that there are certain things which are meant to be beyond our intellectual grasp? All the railing against promising avenues of scientific research because your phony god delusions are offended by the apparent trespassing over an imaginary boundary you've constructed between man and God? All the religious fanatics who protest abortion by saying that all lives are sacred right in the very same breath they use to bomb a medical clinic? All the lies, the ignorance, the pro-stupidity attitudes, the false hope, the immorality in the name of an imaginary being?
The short answer to that is a resounding yes, if you couldn't already guess.
When we get right down to the crux of the problem, it lies in the fact that religious people take what their religions have said as indisputable truth. Sure, people who are crazed fundamentalists take every last word literally, and those who are more moderate don't, but even the moderates take some part of it as being beyond debate... generally, it's the inclusion of some form of afterlife, and some form of superior beings and/or state of being. It's because people have these sorts of beliefs that they do things which are demonstrably stupid and useless and sometimes absolutely harmful. Even the most generic of religious beliefs, which is the idea of an afterlife (whether it be going to heaven or being reincarnated or being carried off by aliens to the home planet or whatever) has the unfortunate effect that people end up too concerned with that afterlife than the life we all really do have. Rather than worrying about setting real-world affairs in order, you worry about being accountable to a hypothetical judgment of some imaginary being for some follow-up path which can't ever be proven to exist. Here's who we should really be accountable to -- EACH OTHER... and that's it! Believers in an afterlife don't seem to get this simple fact, all because you're too damn afraid of death to even pay attention to life.
Why do I speak of gullibility here? The idea of accepting something to be true based on nothing is gullibility. You are believing with no good reason. Faith is the exact same thing. Faith is when you have no evidence, no foundational facts, no basis on which to believe something, but you still believe. And for what? The chance that you might be rewarded for your gullibility after your death? The chance that you could possibly enter a higher plain of existence by achieving some ill-defined condition that others supposedly attained? The hope that there's something special about you that puts you under the scrutiny of something greater than you which may not even exist? These aren't reasons to believe anything, and anyone who tells you otherwise is no friend of humanity. The worst part of it all is that religion and a culture that accepts religion trains people into a mindset that this is a good thing.
If this sounds as if I'm telling you that atheism is an objectively superior position, well... it is. But the real point of the anger over religion is not to chide people and denigrate them, nor is it to posture our own supposed intellectual honesty. It is the expression of our utter disappointment and the horrifying disgrace unto the capacity of the human mind that is embodied in religion. When we "angry atheists" tell believers that they are irrational fools who commit countless logical fallacies, it is certainly true, but there is more to it than that. To distill it down, it comes out a little something like this -- I took the effort to study in depth. I asked questions. I started from doubt and remained entirely committed to a rational survey of the facts. Why can't you? If, in fact, there is objective truth in your beliefs, you have nothing to fear from doubting and questioning, because no amount of doubt can make what is true untrue. If on the other hand, your beliefs are false or have no basis in fact, then it will take very little questioning to expose those failings and you will find that the foundations themselves to built on nothing more than loud noises. Any unwillingness, any rejection of questioning, any fear of doubt, any expression which indicates that faith is valuable is a clear indication that the ideas don't stand up to scrutiny.
I am not the Grumpy Anti-theist because of something your god supposedly did to me. I am grumpy because you, the believer, bring such shame on humanity. I am grumpy because the act of having faith constitutes the highest of intellectual disgrace. I am grumpy because the world teaches those of faith that their gullibility makes them a better person. I am grumpy because there are people out there who want their religion to replace science in schools. I am grumpy because we tolerate the violations of basic principles of humanity in the name of "respecting" people's cultural beliefs. I am grumpy because we have legislators who have the inability to separate what is necessary in reality and how their devotion to fictitious tales of divine sorcery guides them. I am grumpy because we are training future generations not to be part of the future. I am grumpy because we divide people unnecessarily on the basis of the variations that people have on their absurd glimpses of what is anyway untrue. I am grumpy because there are people who are branded as the living embodiment of the spirit of evil simply because we don't exhibit the same gullibility as you do. I am grumpy because of the general inability people appear to have to accept things on the basis of fact and not on the basis of how they feel about it.
I am grumpy because there is a stain on humankind that needs to be wiped out, and the worst thing I can do is to shut up about it. People need to use their brains, talk with their heads, enact policies guided by pragmatic real-world needs. Education needs to actually be... well... education, where children learn to think and reason. People must learn to accept inconvenient truths and reject ALL happy lies and deal with it without shrugging away from it for a second. Intellectual laziness should be the new deadly sin within society. Can't take it? Go suck your thumb and sit in the corner. The grown-ups have to take over.