Just because a large group of people hold a certain unverifiable opinion does not mean it has any more authority or validity than another unverifiable opinion. Even if it did, you've lost that argument already on the basic fact that there are far, far more "theists" than "atheists".

Example: Scientists would want to disagree, but I would argue that the overwhelming number of people in the world who believe in a god (of some form) does constitute a legitimate authority on whether or not something (god or otherwise) does or does not exist.

See how that works?