The average person needs to know that Byron Katie is not just some kooky old lady yacking away. She is a master hypnotist, and mass persuader, very sophisticated and technical.
Its all detailed in these threads.
I'm not sure that "hypnotism" is a term that's ever been rigorously defined scientifically. Surely, for the vast majority of people in this discussion, the words "master hypnotist" conjures up images from old movies, sit-com plots, and Vegas lounge acts. My point here is... to call someone a "master hypnotist" says next to nothing. If anyone gives a teaching that I don't like, I can ALWAYS say, "He/she's is just hypnotizing people." If my sister says she's in love with someone and I don't approve, I can ALWAYS say, "She's not really in love, he just has her hypnotized."
As far as being a persuader... pretty much everyone is persuading all the time. Persuading, after all, is far far better than forcing your views on others.
There is ZERO evidence Byron Katie helps anyone. ZERO.
Just Testimonials, which are not evidence.
There's ZERO evidence that psychiatry helps anyone. We don't even have a definition of what "help" is! That's why each of us has to decide for ourselves what helps our life, and what hurts it. "Help" and "hurt," after all, are entirely relative to what we WANT in life. And that's an entirely personal decision. It's not proven by evidence, so we can't assert objectively what's helpful. We can only try our best when it comes to our own lives, and leave others alone to do the same, as much as possible.
If I feel that, e.g., doing the Byron Katie work has been harmful to me, then I can try to communicate clearly what my experience was, and why I define it as harmful. This gives information to others, who can then make more informed decisions. But the ultimate decision of what's helpful/harmful is made by each of us within our own value-system.