[Serious] Atheist Dogma

[Mr.wizard]

Let's try a different angle, what do you think of an agnostic theist?

I assume you're using the word "agnostic" here to refer to someone who thinks that the true nature of God is not or cannot be known. So an agnostic theist would be someone who believes there is a God (for whatever reason) while acknowledging that we can't know what that God is exactly. 

Is that what you mean? 

Such people are common in the history of Christianity. All the negative and apophatic theologians meet this description. 

Obviously, the way David Mitchell was using the word "agnostic" was different.

No, an agnostic theist is someone who believes there is a god but acknowledges that the existence of god is unknown or unknowable. What god's nature is or what god is, is a separate question all together. You are trying to make Agnosticism synonymous with Atheism, if that were the case then having an agnostic theist would not be possible, because that person would be saying they believe and don't believe in a god at the same time.