Why do atheists deny that they are just biorobots?

[Jackalope]

That's what we've been trying to tell you. Atheism isn't a worldview. It's the result of an epistemological stance.

Here's what confuses me. I have exactly the same epidemiological stance, apply reason to experience, and yet I reach a different conclusion, i.e. God exists. Why then, is my belief in God a worldview and your opposite conclusion not one?

It isn't.

Theism isn't a worldview any more than atheism is. Your specific flavor of Christianity is, however, as is secular humanism.