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

[abaris]

But the ones who do are usually engaged in actively taking a stance against atheism, and since in their view atheists are all also necessarily anti-theists, they try to equate atheism with religion to make them angry.

Have you ever thought that they simply can't wrap their heads around someone not following some hidden code in their lives? In my opinion, that's the main reason. Not understanding that absence of belief doesn't mean swapping believes.