I am so impressed, that you are capable of hanging a label on the man that he himself didn't think was a proper description of his beliefs. I guess you know more about his thoughts than he did himself.
Meaningless.
Michael Schiavo doesn't consider himself to be a murderer. John Gotti considered himself to be a "business man". So what? We all must accept their image of how they see themselves?
Russell's estimation of his own pigeon hole was as fallacious as most of his other beliefs.
Got a problem with me? Then you have a problem with the atheists, too. He is considered, in atheistic circles, to be among the Patron Saints of Atheism
In any event, whether atheist or agnostic, it is indisputable that he was hostile to organized religion.