easiest way to identify a cult is by the absence of people who openly criticize the culture of the group

there can always be some who try to drag the group into groupthink and some prescribed set of doctrines, and into a "true Somethingers" group but when the critics don't get completely driven out, via malicious actions, you can be confident that the cult mentality in a group is too weak and that probably that is because of precepts of the group meme set are counter-cult...

yes, allowing critics is a counter cult doctrine... there are others as well, but it's a key one