# followers of an exclusive system of religious beliefs and practices
# fad: an interest followed with exaggerated zeal; "he always follows the latest fads"; "it was all the rage that season"
# followers of an unorthodox, extremist, or false religion or sect who often live outside of conventional society under the direction of a charismatic leader
# a religion or sect that is generally considered to be unorthodox, extremist, or false; "it was a satanic cult"
None of these fit atheism.