Religion (www.dictionary.com):
1.a set of beliefs concerning the cause, nature, and purpose of the universe, especially 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.
Atheism:
1. The doctrine or belief that there is no God
2. Disbelief in a Supreme Being or Beings
Based on the definitions listed above, no, Atheism is not a religion in and of itself.
However, I do believe Atheists sometimes mobilize themselves in the way Christians do in defense of their beliefs (which, by the way, isn't an absence of belief; it does not acknowledge a Deity, but it is still a belief in the fact that there isn't a Deity).
Also, I really wish some religious leaders weren't so ignorant of their word choices. "Liberal" does not mean "secular" by any definition of the word. People who interchange words that have nothing to do with one another really need to know what they are saying before making public comments.