It all depends on how you would define religion doesnt it? It doesnt have to pertain to a God or gods. So we could argue this forever, but which on do you think atheism falls under hmmm....
re·li·gion
 
 /
rɪˈlɪdʒ
ən/
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uh
n]
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noun 1. a set of beliefs concerning the cause, nature, and purpose of the universe, esp. when considered as the creation of a superhuman agency or agencies, usually involving devotional and ritual observances, and often containing a moral code governing the conduct of human affairs.
2. a specific fundamental set of beliefs and practices generally agreed upon by a number of persons or sects:
the Christian religion; the Buddhist religion.
3. the body of persons adhering to a particular set of beliefs and practices:
a world council of religions.
4. the life or state of a monk, nun, etc.:
to enter religion.
5. the practice of religious beliefs; ritual observance of faith.
6. something one believes in and follows devotedly; a point or matter of ethics or conscience:
to make a religion of fighting prejudice.
7. religions
, Archaic. religious rites.
8.
Archaic. strict faithfulness; devotion:
a religion to one's vow