There is a saying, perhaps it was just a remark, that getting Atheists to agree on anything is like trying to herd cats. I believe I have an understanding why this is so.
With religious cults you have the dogma of that cult to bind people into a pattern of thinking. Depending on the particular cult involved the minds of the group are molded by the leaders’ interpretation of the doctrine. From a very young age malleable minds are repetitiously "programmed" into predictable thought patterns. Once this indoctrination has solidified it is rare that someone can completely break the "spell". Even if the spell is broken, mental powers may remain forever damaged, still influenced by archaic thoughts.
Atheists are another consideration entirely, especially if they are able to remain uninfluenced by religious dogma. Atheists opinions are infinite on myriad points of conjecture. To organize they must realize that the best they can hope for is a percentage of agreement. To expect total agreement on anything except the most basic things is to accept the literal fact that there will never be an organization wherein energies and monies may be directed to promote freethought. Atheists, express your opinion, but do not expect total agreement. Or nothing will ever get done!