May I ask for a list of these reasons?
1. Different religious belief systems make contradictory absolute claims. They can't all be right. Probably they are all wrong.
2. If you were to make a list of basic human needs, you might start with oxygen, water, food, warmth, shelter, human companionship, and so forth. Where in that list would you write that you need to know a man was nailed to a tree 2000 years ago because you were born with a need to be fixed, in the opinion of an invisible being? It's not a credible human need.
3. People don't walk again after being executed. People are born of two biological parents. People don't walk on the surface of water without support. The claims of christianity are absurd, and there is no good reason to believe they are true.
4. Prima facie, the god claimed in christianity isn't really there.
5. The quality of knowledge gained from methods used in disciplines like the sciences or history can be shown to be high. The quality of knowledge gained from assertions based on being spoken to by god(s) or from 'revealed' scripture can be shown to be low.
6. If you are interested in explaining anything properly, then special claims about Jesus or gods never increase the quality of the explanation. There is no explanation at all in god claims, and not much more than standard human social interactions / claims of insanity (by C.S.Lewis, for example) when it comes to Jesus.
7. It's just not very interesting. The fact that people believe it is interesting, but the mythology of Jesus is that of just another Mesopotamian man-god belief system, like all others of that kind.
8. There is nothing special about resurrection in scripture. Lots of people came back to life, and of course that is probably a commonplace claim for ignorant ancient goat-herders and fishermen.
9. There is nothing remarkable about the Judeo-christian scriptures. They are historical fiction, and contain nothing that indicates inspiration by any kind of 'all-knowing' mind. There are hand-washing rituals in the Jewish bible, and sometimes those rituals would help with hygiene, but at other times they are pointless. Imagine if Deuteronomy contained a statement like: "You should wash your hands before eating because there are things on your hands too small for you to see that will make you sick'. Wouldn't that be astonishing? Well, there is nothing like that in any part of scripture.
10. The proposition of christianity is immoral. Compulsory love on pain of burning in sulfur. A totalitarian system worse than any of the excesses of communism or Fascism.
That's just 10 of my reasons. I do have more. Thank you for asking.
Also, if you are so big on researching word usage, "Atheist" shows a peak, highest peak, usage in 1801. So, what is your point there?
Well, you raise a fair point, and I am surprised that the Google book search has the usage of the two words about level-pegging throughout the decades.
But I don't feel the need to defend the word atheist. It is an accurate description of the way I live my life, but I don't like to define myself in terms of the religious delusions of others.
The term atheist probably has a lingering bad rap in the US because McCarthyism associated 'atheist' with 'communist'. It seems to me that 'unbeliever' is used more deliberately as a pejorative term by religious enthusiasts.
Stuart