Sentence:  Throughout history, <WSD>atheists</WSD> were simply people who did not believe the prevalent God of the day. For the sun-worshippers, Christians were <WSD>atheists</WSD>. For Jewish people, Christians were <WSD>atheists</WSD>. Whoever does not believe in your God is by definition, an <WSD>atheist</WSD>. ... With all the countless Gods concocted by man, I claim that my Christian friends and I have something in common. We are all <WSD>atheists</WSD>, I just believe in one less God than they. 
Meaning of the word marked with <WSD> tags:  A person who does not believe in a particular deity (or any deity in a particular pantheon), notwithstanding that they may believe in another deity.