A (no) - theo (God) - ist (person who holds this opinion)
Thus the word "atheist" merely asserts a negative connotation about the beliefs of others, and in no way asserts anything positive about anything. By that criteria, the name atheist actually qualifies as hate speech. http://en.wikipedia.org/wiki/Hate_speech
Since all religions since time immemorial have always asserted some form of positive reality, correct or not, they didn't build social structures on the lack of, or supposed non-reality of something that others positively propose. Atheism's very essence is the antithesis of what religion is.
The word "atheism" was originated about 400-500 years ago.
That word, "atheist" is actually predated by about 2,700 years by another word for the exact same idea. In about 1,000 BC, the writer of the Psalms in Psalm 14:1 uses the word "fool" for one who says there is no God. Having historical precedence, the word "fool" is actually a more valid word to use when referring to an anti-theist.
Now consider the word, "stupid" which is defined as "wilful ignorance", or the "inability to understand". Since God exists, and is revealed in creation, and is asserted by so many people everywhere, anyone choosing to say to themselves that there is no God is either refusing to learn about Him, or is incapable of learning about Him. That makes "stupid" a correct word to use when referring to such persons.
Therefore, atheists are essentially "stupid fools" engaging in "hate speech".