What exactly is atheism? Before I discuss the arguments we get from theists (i.e. people who believe in gods and the religious dogma they get from their holy texts), I would like to point out that it is not a a religion.
A religion is defined by sociologists as:
1) A standardised belief in some or other deity and the worship of that deity;
2) A dogma around the practice of the belief in that deity;
3) A set of rituals of ceremonials that involve the worship of that deity; and
4) The appointment of a hierarchy of - mostly men - to decide on the rituals, dogma and process of practicing the worship of the deity.
So, looking at these points:
1) There is no standard for atheism. A popular meme is that trying to standardise atheism is like trying to herd cats. There is also no deity worshipped by atheists. Most people who declare themselves to be "atheists" regard all gods as mere mythical beings, not to be believed in as real, or to be worshipped.
2) Thus there is no dogma. There is no decided standard, because there are people who do not believe in "God" but who do believe in alternative medicine and astrology and that global climate change is a myth. There is also no trademark on the term "atheist," the only possible way that someone may identify themselves publicly as an atheist would be if they adopted the "A" symbol as an avatar or wore it on a t-shirt. Mostly we don't wear identifying symbols.
3) There are no rituals involved, unless writing weblogs or books is a ritual. Atheists do tend to write a lot about why they don't believe.
5) There is no hierarchy. Richard Dawkins, Sam Harris are not our priests, and Christopher Hawkins would spin in his grave if anyone dared to declare him a "saint."
Now, having got that out of the way, and having demonstrated that it is not a religion, I shall continue to debunk some other memes that abound on the internet about atheism.
1) Where do we get our morals? Humans and most other animals are born with innate morality. Even apes in the jungle have to be taught to murder members of their own species. We don't need to be taught morality, it is a natural part of being a sentient being, as may be seen from the thousands of images on websites demonstrating how other animals take care of the young of other species. We are taught to be immoral by our nurturing. People who are natural killers are called "psychopaths" and "sociopaths" by psychology, and usually they are that way because they are taught to be cruel by their upbringing. Most children have a natural empathy. That is where we get our morality, and it is that which prevents us from committing crime.
2) We are not "rebelling" to "make a point." Nor do we want to outlaw religion or "believe" in some alternative belief system, as demonstrated in my explanation above. Most people who have used their disbelief in deities to expand their learning into other fields, also tend to use critical thinking in their learning and thereby to question everything they are taught, asking for "evidence" before they'll accept what they are told. Religion teaches people to close their minds to conflicting evidence, but to blindly accept whatever they are told, particularly that which is told to them by other religious people. When they say that they "question," what they are told, they usually mean that they question what disbelievers tell them. Questioning what you are told, especially about religion, is evidence of open, rather than closed-mindedness.
3) We don't have to prove that "God" doesn't exist. We didn't invent him, nor do we believe he exists, therefore atheism does not have to prove the non-existent any more than people who don't believe in Santa Claus have to prove that he doesn't exist.
4) We are told that "most people believe in God" and that we are "surrounded by evidence" for him, with the human eye being cited as that evidence. To refute this, I shall quote my mother who used to say "if most of your friends jump off a cliff, would you do it too." Just because large numbers of people believe something, it doesn't make it true. Also why the "human" eye, why not the eyes of bees, or birds who have far better sight than humans? If human eyes are so special, how come they deteriorate at a very young age? Most modern humans have to have assistance with their sight by the time they are in their middle 30s. How does the "greatness of the human eye" account for cataracts and sun-blindness? God did not create the mountains, or the forests, mountains were created by the movement of the tectonic plates, and the world's forests evolved from the first plants that took root millions of years ago.
5) What is the reason for your life? Aren't you afraid of hell? Why don't you just believe, just in case (Pascal's Wager)? The answers are simply: there is no reason for any animal's life except the perpetuation of the species. What is the purpose of a life that dies at birth? There is no purpose, you were dead before you were born, you'll be dead after you die. All the eggs your mother expelled in her menstrual flow or in the dozens of lost pregnancies throughout her life (yes, a lot of fertilised eggs are expelled as menstruation - google it) and the eggs that weren't fertilised and the other more than a million sperm cells expelled by your father in night time emissions as a teenager and during intercourse, they were all prospective life. So what was their purpose? As you can see, I don't care about hell, because when I die, I'll go back to being the stardust I was before I was born.
6) Hitler, Stalin, Pol Pot, were all atheists! No they were not. Hitler's soldiers wore a badge on their uniforms that said "Gott mit us" (God with us), Hitler himself invoked the name of Jesus in many of his speeches, especially in rants about the Jews being "Christ-killers." The other two were communists, their religion was communism. They merely replaced "God" for a hammer and sickle, their churches were the offices of their tyranny and their priests were the people who carried out their bidding; in the same way that the Pope sits in the Vatican and sends out priests to carry out his instructions in their cathedrals and churches. They were not "atheists" because they rejected "God" who they believed was real, and replaced the worship of him with the worship of their ideology, and Karl Marx.
7) The devil, prayer, hell, etc. do not exist and they do not work. Being an atheist does not include the worship of the devil. We do not pray and personally, I've recently have evidence of its inefficacy when people "prayed" for me to sell my house and someone else "prayed" for me to be cured of my chronic illness.
8) "If you read the Bible, you'll change your mind." As may be seen from this website, I took on this challenge. Rather than change my mind, it confirmed what I'd always thought: that the Bible was based on ancient mythology and that the deity in the Bible was evolved from the deities worshipped by the people whose mythology was adopted. He emerged from the El of ancient Ugarit, Babylon and Canaan to become the JHWH of the Old Testament and later the "God the Father" of Christianity. Reading the Bible from cover to cover is more likely to cause you to stop believing in God than to strengthen your belief.
9) There are no atheists in foxholes. Having never been in a foxhole, I do not have enough personal experience to comment on this, but I do have a lot of friends who were soldiers during WWII and most of them say that being in the war was what killed their belief in "God." They say that they can't worship a God that would allow that sort of atrocity to happen.
10) Finally, because I'm obsessive about round numbers. Far from being "intolerant" of religion, personally I am extremely tolerant of people who blindly follow religion. I have a fairly large extended family, some of the members are atheists, others are ambivalent about it, others have some sort of spirituality that they don't discuss, others are devoutly religious. I don't try to convert them. I don't even suggest that they read my blogs, although I read theirs, and comment on them. I have friends who have all sorts of beliefs, and we discuss their beliefs without rancour. They call me a "militant atheist" and that I sometimes come across as "arrogant" which makes me smile because apart from being passionate about the things I enjoy discussing, I mostly live and let live. Far from being arrogant about my knowledge and non-belief, I am rather insecure because every time I learn something, I realise how little I really know. I also know that most of my atheist friends don't go about ringing people's doorbells asking people to "convert" to atheism. Which is a lot more than I can say about theists.