Just a note that for thousands of years atheism was 'a pretty extraordinary claim'.
Its the perspective of the hearer brother. To the majority of the world, atheism is an out of the world, impossible, extraordinary claim. In 2013, unless I have got my figures wrong, around 53% of the world were either Quran or Bible believers, and then you get all kinds of other theists. Hindus are a huge population in the world but they dont come into conversation much because most of them are in one country. So most of the world are theists.
Both claims, theism and atheism are extraordinary claims to the recipient. You are right. I would add though that in some parts of the world there were discoveries that made it evident that in ancient times there were certain people who seem to be atheists. I know of one finding in a country called Sri Lanka where they discovered a tribe of people who lived on lizards for food called Niththawo. They dug up a lot of discoveries but there were no shrines, deities, zilch. Generally you do any kind of archeological research on any society you find gods and many signs of theism. So the absence of them are very good indications that they were atheists. Thus, atheism is supposed at least go back to 300 - 500 BC.
Also, Buddhism is very much misunderstood. If you go to the main or the most authentic and fundamental scripture of the Buddhists, it is the Tipitaka or the Thripitaka. To find theism in these books one has to do inference so its difficult to get theism out of these texts. Also, where ever there are small signs of theistic or deifying texts, they are out of character. As if its an advertisement in the middle of a movie. Out of character. So scholars like Gombrich and some others say that they must be latter additions. So bottomline is, originally, Buddhism seems to have been a very atheistic philosophy and focuses on self actualisation rather than salvation.
Anyway now I am derailing the thread it seems but I have typed to much to delete this.