I think you're setting an unnecessarily high standard for the usage of this term. 'Cult' is used to describe a group with very extreme, zealotous views who venerate a certain person. It can, and often is, used even looser than that.
Here are some examples of that found with Google:
- Cult Archaeology and Unscientific Method and Theory
Is Graduate School a Cult?
Why would anyone in their right mind want to join the vegan cult?
I can only imagine that you are nitpicking out of your own veneration for Bernie.