The Atheists and their allies/cousins the Secular Humanists, and their masters (the Discordians) will swear up and down that they are not a 'Religion', but they are just as much a Religion as Christianity, or Judaism, or Islam, or Hinduism. It’s just more difficult for them to turn your government into a Theocracy if they tell you this in advance. Deception, obfuscation, and misdirection are inherent to their nature.