I think the term 'anti-theist' carries with it an interest to act. Maybe I'm wrong on that one, I don't know, but I feel the term would be suitable for e.g. the four horsemen of atheism who are/were actively on the frontlines seeking to deconvert and make things 'right'.
"It is the mark of an educated mind to be able to entertain a thought without accepting it" ~ Aristotle