I agree on the conclusion (atheists are religion), not so much on the why (the things they revere).
I would argue they are a faith based religion because atheism implies certainty or strong conviction towards the lack of a god. Since god is not falsifiable it requires the same amount of faith to claim he is real as it takes to claim he isnt. Therefore atheists are faith based. Only an agnostic, someone who makes no assertions about a god's existence, can truly claim a non-faith based opinion.
Sure, both groups are claiming something though, atheists are claiming there is no god, theists are claiming there is. Both have a burden of proof, neither can show it.
The only person without the burden of proof is the agnostic, the agnostic is essentially saying "I've heard both claims and have no evidence to accept either of them". So the agnostic is the only person without a claim and thus the only one without a burden of proof.