Why do religious people desperately want to class Atheism as a religion?

[RobbyPants]

It's a tactic.  The argument goes something like this:

Atheism is a religion in that it is a worldview and a belief that no God's exist.  Atheists claim that it is simply a lack of belief in the existence of any God and then Theists will define it as believing there are no Gods.

This is used to shift the burden of proof the atheist to prove there is no god.

If I mention a lack of belief due to a lack of evidence, they'll say they "lack a belief in the big bang", and then bust out some old, tired watchmaker arguments.