I think there are basically two types of atheists. There are those who were never hot on religion or never acquired religion in their lives. They are sort of relaxed and laid back and just couldn't be bothered by the religious debate. Then there are those who converted from religion to atheism. Initially they are enraged when they realise how they had been indoctrinated, brainwashed and consequently how their true potential and talents had been diluted by dogma. They are scathing and aggressive in their comments on religion which they experience as a personal affront. This is just a phase though because with the passing of the years their attitude mellows although they remain as irreligious as ever. That being said, the crude satirising of religion is just as important as an intellectual dissection or logical/philosophical critique because the religious audience varies from the crude to the intellectual.
Today the ranks of atheism are swelling because information has become more accessible, courtesy of the internet and devices such as the smartphone which places the world's knowledge in the palm of your hand. Religion on the other hand thrives on ignorance. Most new atheists are converts from one religion or the other when they realise that the dogma which had governed their lives is a fairytale. This does not imply that religion is on the decline, on the contrary, because religiosity increases with suffering and suffering is on the increase in the world. I think Pope Francis, for example, realises this and that is why he is taking the Catholic Church by the scruff of it's neck back to the poor.
Contrary to general opinion, atheism is not a belief system, but a total absence of it. Atheists do have a cause though. Atheists demand equal treatment. In many parts of the world an outspoken atheist would be killed or tortured or incarcerated at worst, or discriminated against or ostracised at least. A simple experiment would suffice. Go hiking through Africa with a banner reading "Forefathers Suck" and see how far you get before a mob tears you to pieces. If walking doesn't appeal to you, drive a car through the USA with the slogan "God is Gay" painted in pink on it and see how far you get before a redneck fundamentalist blasts you to kingdom come with a shotgun. Substitute the slogans with "God is Great" and no one will touch you.
The second part of the atheist cause is to dilute religion, because falsehoods spawn more falsehoods. If I may speak for atheists, they have no problem with what a person believes, as long as it does not impinge on the right of others to think or believe as they wish. Unfortunately most religions are missionary by nature and this makes them dangerous. Most religions will tell you that their doctrine is peaceful and about love. This is a half truth. The love is reserved for those who believe exactly as they do, the rest are outsiders or infidels. The outsiders are discriminated against, labelled as evil, dehumanised and scapegoated. Examples are legion. Gays are hated. Women are property. Muslims are the enemy. Forefather believers are barbaric. The Chinese are all going to hell. Protestants are not christians. The Jews killed Jesus, etc. At worst this could spawn wars and genocide, of which the Holocaust and the Rwandan massacre are prime examples. It can give rise to discriminatory legislation such as the anti gay laws in Uganda or Apartheid in South Africa, which had a fundamentalist religious basis. On a personal level it allows the believer to duck responsibility of which a good example is Hansie Cronje's "the devil made me do it". Religion requires children to be targeted, brainwashed and to develop guilt and existential fear. This is a form of child abuse because the child will carry the mental scars for the rest of its life. We should teach our children how to think, not what to think. Right here in my area are adults who were prevented to read anything but christian literature when they were kids, and it shows.
The good deeds that religions do are to be applauded though. Every soup kitchen and every jersey knitted for a child is wonderful, but the motive is immoral if the idea is to buy timeshare in heaven or gain more converts. These people will never know the intense satisfaction derived from doing a good deed out of an innate sense of morality and not because it is dictated from outside by some god. Atheists that I have met are the most moral people I know. Their sense of right and wrong is so finely honed that it can be irritating in general society. Coupled to this an atheist takes personal responsibility for his/her actions. They have no excuses like they had been created as sinners or they were tempted by the devil.
At this stage the question of humility comes to the fore. The religious contend that they are the humblest of people because they are as nothing before their god. But if they believe that the allmighty creator of the universe has a relationship with them as individuals, its not very humble, is it? The atheist on the other hand sees himself as a higher order primate and a total insignificant speck in the context of the cosmos and geological time. That's humility.
I have never come across an atheist who fears death. The manner of dying maybe, but not death itself. They understand intrinsically that when they are dead they cease to exist, so it makes no difference whatsoever. The religious on the other hand, live in constant fear of death and worry their lives away about what will happen to their souls in the aftermath. It pollutes their lives. Atheists do not live in fear of demons, angels, ghosts, devils, forefathers, gods, or anything supernatural. Because of this the atheist must have a better quality of mental life.
An atheist does not have the ability to believe something which is not true. Religions on the other hand do not require facts to exist. This is why for example, a scientist can not debate a creationist. The creationist just says "I believe the earth is 6 000 years old" and no facts will persuade him of anything to the contrary. To believe in something it need not be true. The religious will vehemently defend their religion, in some cases even with force, but they can not provide a factual basis for it. The atheist requires the pie to be baked in the oven, not in the sky.
In conclusion there is a distinction to be made between atheism and agnosticism. For the sake of brevity I quote the Oxford English Dictionary. Atheism is the disbelief in the existence of a god; godlessness. An agnostic is one who holds that nothing is known, or is likely to be known, of the existence of a god or of anything beyond material phenomena. This article probably explains both approaches since both debunk religions, although agnosticism allows for the possibility of the existence of some god or other.