Their fatal flaw is assuming that cults are inherently hierarchical, which isn’t true. Though it’s true that most popular cults do revolve around a prominent figure who is provided power (I.E. the cult leader), there are plenty of cults centred around documentation, philosophy, etc. and don’t exhibit a clear power structure.

I’m not going to say Anarchism is a cult, but it is not diametrically opposed to cultish behaviour. This can be seen on full display on the online left and their dogmatic approach to dialectics.

You can also argue that literally all politics are “cultish”, because the qualifier for something being a cult is defined as “a group or movement held together by a shared commitment to a charismatic leader or ideology. It has a belief system that has the answers to all of life’s questions and offers a special solution to be gained only by following the leader’s rules.” If Anarchists are going to argue that we’re cultists for our upholding of Marxist philosophy and scientific socialism, then they should look in a mirror, because they do the same with Anarchist philosophy.