I can't speak for other atheists, but personally, I don't "assume" that religions are false, I look at the evidence that I can see, and I make a judgement on whether I think they have any merit or not. And so far, every religion presented to me has failed to pass my standard of truth, with either blatant contradiction, or just plain lack of evidence. If you can prove to me that your religion is true then I will convert to your religion. I am not closed to the possibility of a God existing, I just know that the gods of today's modern religions cannot exist, because their holy books and their sects are all extremely vague and contradictory on what their God actually is.
If you do not believe in a spiritual being but acknowledge the possibility of one, you are not atheist but agnostic.
lotr rocks 0 said:
Also it is extremely naive to think that some two thousand year old book written over the course of hundreds of years is the only source of morality. Morality is socially constructed, it is not divinely constructed.
If there is no God, god, goddess, etc. then there can be no all encompassing moral truth. This means that, since after we die according to atheism, we all end up as nothing, there is no point to being moral because we all end up the same in the end. Now, I am not saying that the Bible, the Quran or whatever other holy book's morality is the truth. It is that the acknowledgement of a moral truth that exists beyond human understanding makes us strive to be as moral as possible. Moral laws are created by society as a direct response to our yearning for an ultimate moral law, so while this moral law may not exist, if we do not acknowledge it's existence, our laws are meaningless.