Most atheists lie about their "unbelief" because they cannot reconcile their presumption (belief) that gods don't exist with their complete inability to produce any evidence to support it.
There is plenty of evidence that all gods are the creations of man's imaginings. Even you would have to admit that Atlas and Shiva and Oshun are not really God. Even you would have to admit that Atlas and Shiva and Oshun are the creations of man's imaginings. You, like all other theists, make one and only one exception - your own god - although there is no rational reason for doing this.
On the flip side, there is no evidence that JesusGodHolyGhost, Allah, Atlas, Shiva, and Oshun are really God. There is nothing that cannot be explained by natural causes.
More evidence that Gods are the creations of man's imaginings is the fact that all Gods (supposedly) look like the people in whose imaginations they were created.
Even as they constantly demand that theists produce evidence to support their presumption (belief) that God/gods do exist. They are hiding their blatant hypocrisy (from themselves) behind this lie about their "unbelief".
I don't ask theists for evidence to support their versions of Gods. I don't think most atheists as for evidence. In fact, if you look back a few posts you will see another atheist recognizing that theists work on beliefs and blind faith.
There isn't anything anti-theist about the concept of blind faith in religious beliefs - as theists are actually proud of the fact that they invoke faith to believe those religious claims. They consider it a virtue.
I do occasionally ask for evidence of some of the things their god supposedly did, like The Great Flood. There never is any. I do occasionally ask for evidence of some of the things their holy scripture states like The Exodus. There never is any. I do occasionally ask for explanations of how some of their beliefs could really be true. For instance, how was Matthew able to quote, word for word, the Sermon on the Mount. For instance, how could Shogi Effendi be privy to the detailed conversations Ballula ostensibly had with Highest level Government officials. There never are any good explanations.