Ybe an atheist

[Angrboda]

You’re misunderstanding my position. Atheism is the default for anyone who doesn’t believe in any gods. It’s impossible to be a theist or a deist if you don’t believe in god.

(Above bold added by YBe)  "Atheism is the not the default for anyone who doesn’t believe in any gods". [now it is true]

OK this is a serious Q, just think before you answer please. Will you please kindly, verify logically, rationally that your position is rational. 
And then also give proof that the statement "It'is impossible to be a theist or a deist if you don’t believe in god". Cannot be false".

If you keep just making the assertion as if you think that it is proof, then   accept this assertion as absolute proof for you
 "atheism is irrational".  > Re-asserted <, so it cancels all of your future ( unproved assertions).

The analytical meaning of the terms theist and deist is that one such doesn't believe in any gods. It is an entailment of what the terms theist and deist mean.
Regardless, the proposition that atheists are irrational is not at all the same type of proposition, so your argument fails.