Answer to the OP: nothing.
A stage hypnotist gives people suggestions, and provides a safe, relaxed, fun and enjoyable context in which they can go along with or play out those suggestions if they wish to. That’s it.
Okay, thanks for your assertion that anyone who disagrees with you doesn’t know about the subject. Just since this is all about fighting ignorance, let’s swap credentials shall we?
I’m a professional performer myself and a member of the Magic Circle. I’ve never specialised in stage hypnosis, but I have used it occasionally in my work both formally and informally, and I’m well-read in the pertinent literature.
I expect I personally know more working stage hypnotists than you do, and a bit more about what they do and how they do it. I’ve had conversations with several of them, in the UK and the US, spanning many years. I could probably pick up the phone right now and talk to at least 12 friends who have performed stage hypnosis professionally. Your total?
One of my closest friends has earned a living from stage hypnosis for over 15 years, and was called at an expert witness on the subject at a test case legal trial conducted at the Royal Courts of Justice in London, which I attended. I know from having discussed precisely this point with him that he would agree with my answer to the OP.
I’ve read some of the so-called skeptical literature, such as ‘They Call It Hypnosis’ by Robert Baker, and I’ve met some of the leading investigators who have looked into the very point mentioned in the OP, such as Joe Nickell. Baker and Nickell would agree with my answer to the OP.
I’ve also attended and enjoyed many stage hypnosis shows over the past 20 years. I’ve never seen any evidence which would suggest my answer to the OP is incorrect.
But of course, the possibility remains that I’m wrong and you’re right.