Why do atheists deny that they are just biorobots?

[robvalue]

Atheism is simply a lack of belief in god claims. That is the definition.

You can't base a conclusion on a lack of belief in an outlandish claim, other than the conclusion that the claim hasn't met its burden of proof. You are trying to connect atheism to other ideas, and that is faulty. If an individual atheist makes a positive claim about belief, it stands or falls on its own merits and has nothing to do with being an atheist.

What conclusions are these you are talking about, that atheists don't back up when pressed?