That link leads to cultwatch list of things a cult tends to do. I often find it interesting how many of the requirements are fulfilled by some martial arts organisations.
Deception used in recruiting? People talk about martial arts alllowing you to beat bigger stronger attackers -and then on the inside it is sometimes the case if this is true it's only after a loooong time...
Exclusivism. I know from experience how martial arts organisations can react negatively to students who cross train, be it in other arts or other styles of the same art.
Fear and intimidation - members fearful of disagreeing with leadership. You certainly see that in some strict traditional arts.
Love bombing and relationship control. New students sometimes will be 'love bombed' (although not necessarily consciously and it's probably just a sign of a good culture). Relationships start to be focused more and more on people inside the group? certainly you sometimes see an element of that.
Information control - impossible in the connected world. But I've certainly heard people discouraged from looking into other arts, ways of thinking
Time Control. Classes, gradings, seminars, solo practice dojo events. Oh yeah check that box we all know how quickly martial arts can start to take up your time.
That's not to say actually think martial arts are cults - for the *most* part these things happen without the intent of mind control. It just amuses me that if someone wanted to make a case for a martial art being a cult there's plenty of ammo there....