Whether or not it is you or your audience, you barely (if at all) attempt to explain what you mean in a step-by-step process that would clarify the whole thing for everyone. Since you are not doing this, and since you won't provide references... anyone can say stuff. Just saying it doesn't make it true.
I did explain it step by step.
Let's do it again.
You say religion is "a set of beliefs concerning the cause, nature, and purpose of the universe" and you say atheism is a religion. Atheists do not have beliefs about the purpose of the universe. If they did, they could not be atheists, since a purpose or reason for the universe demands a creator. Therefore, atheism is not a religion.
Which part of that train of logic don't you follow?