There’s still the difference between religion and cult. Size matters not.
A cult, in the somewhat bastardized definition that has gained popularity in recent years in the USA, is simply a religion generally viewed negatively by others.
And I’m happy to agree that the negativity is often well-justified. But I hope you will agree that we don’t want to make legal distinctions on this basis.
Do you really think it would be a good idea to make legal distinctions by which “cults” are stripped of the protections afforded recognized “religions.” What government agency would you like to put in charge of deciding which groups will be recognized?
Much better, to my mind, to give legal status as religion to any group claiming it, no matter how kooky their beliefs. This of course should not inhibit us from fully enforcing laws they may break. Beliefs are and should be no business of the State. Actions are and should be.