- The words “atheist,” “atheism,” “atheistic,” etc. are not capitalized unless they are at the beginning of a sentence.
- "Atheist" is not an adjective. The word "Christian" works as both a noun and an adjective, so you can say things like "I’m Christian" and you can refer to yourself as a Christian. That is not the case with the word "atheist." You can’t say "I’m atheist," it’s "I’m an atheist." If you must shorten it to two words it has to be "I’m atheistic," although that’s kind of weird. The word "agnostic," however, can work the same way as the word "Christian," so you can say "I’m agnostic." (Side note: atheism and agnosticism are not mutually exclusive in the slightest).
- "God" should be capitalized when it is used as a proper noun regardless of whether or not you believe there is a god (note that in this context the word "god" was not a proper noun and I didn’t capitalize it). You can say "I don’t believe in God," or you can say "I don’t believe in your god." The first implies the Judeo-Christian god who is, for our purposes, named God. If it helps, think how you would phrase it if you were referring to Zeus. If you would use the name "Zeus" then capitalize it. If you would still use the word "god" even if the god you’re referring to is Zeus (the god, a god, your god), then don’t capitalize it.
- I refuse to capitalize pronouns unnecessarily. I know that some Christians capitalize the word “he” whenever it refers to their god. I will not participate in this foolishness and you can’t make me.
Any objections? Any grammatical pet peeves you want to add?