In the split, a New York branch of the group lambasted the Sunday Assembly's marginalization (ironically) of atheists, calling the group a "humanistic cult."
MORE: http://www.religiondispatches.org/dispatches/sarahposner/7500/an__atheist_church__schism/
See also...
After a schism, a question: Can atheist churches last?
http://religion.blogs.cnn.com/2014/01/04/after-a-schism-a-question-can-atheist-churches-last/comment-page-9/
Sunday Assembly: A Church For The Godless Picks Up Steam
http://www.npr.org/2014/01/07/260184473/sunday-assembly-a-church-for-the-godless-picks-up-steam