The old "kill-the-Ego" gag is one of the oldest, most destructive aspects of these kinds of pseudo-philosophies.
There are some more ancient monastic traditions in Buddhism that hold onto these ideas, and are actually rather "attached" to non-attachment to their own Ego.
I am interested in your remark of the 'kill-the-ego', even as it is in Buddhism, being a destructive aspect. I do understand that here the topic is this Sedona method, and dangerous cult practices, and in that sense you are not talking about traditional Buddhism. But as you mentioned their monastic practices too, I hope this off-topic question is acceptable.
Little background: I've gone thru a colourful enough life of a lot of work, fun and parties, which I still enjoy, being an atheist / agnostic, and somewhat a researcher too (in information technology) and interested in science. During the past few years, however, Buddhism has been growing onto me and I've started slowly practising it the little I can, mostly based on information in the books about it that I have been able to get. I feel that I'm still very early on in
this journey, but also that have read a lot and have at least a vague overall understanding of those teachings, plus some personal experiences from observations during meditation and how it has affected life.
My position so far has been that the idea of 'non-self' or anatta, as the Buddha taught it, is as essential today as ever for the mental development and well-being of people. As I understand it, the Buddha did not deny of there being some sort of conceptual entity in a moment that can be characterized as a 'self', but instead recognized it as a valid tool we need in talking about people and actios in everyday life. But the point is that such a self is not real, in the senses that it would somehow persist unchanged over time, and that it would be a singular thing -- as far as I know, those ideas are in line with contemporary psychology: personalities change and are sums of many elements within the mind.
Also I find that the notions of unity, of us not being really separate from others and the world, nor being really unique either (perhaps every consciousness is basically similar in the end), are fruitful and healthy. If you consider you being basically the same as others, the golden rule rises easily.
Of course, as Buddhism is scepticism, as it urges everyone to not believe anything without observing it critically yourself, it is very much opposed to the cult abuse of the idea of non-self where victims are lured to uncritical acception of ideas. And you did separate the actual idea from abuse in your post too, so I'm not accusing you of anything - mostly just being curious and sorting this our for myself here too, so I hope you don't get me wrong.
This kind of thing has no place in modern society, and modern psychology. This idea of Ego-death, literally is a form of Cognitive Suicide, its very very sick.
Anyhow, as you seem to so strongly state that the ancient Buddhist idea of 'killing the ego' would have "no place in modern society, and modern psychology" and it being sick, I am interested in getting some references for studies, theories, essays or anything on the matter. Or of course your personal views if you are interested in discussing. So far my view is that nothing in our contemporary lifes justifies attaching to a wrong kind of an illusion of a self, not any more than 2,500 years ago -- perhaps vice versa, if/as the societies have developed to be more individualistic and ego-centric, even. But this is a very much non-trivial topic for me and I hope to learn more about it.
Concerning your remark, and what seems to be a strong theme in contemporary western psychology in general, of the wonderfulness of having "healthy, assertive ego-strength": in my understanding of the Buddhist view this would translate to having a strong coherent view of the world ('right view' is the first element on the eight-fold path), and a trained peaceful mind to deal with issues .. without the need for an ego, nor emphasizing individualism. But I guess having such a strong position could be also called having 'assertive ego-strenght', so perhaps to some extent this is just about differing definitions of concepts / semantics.
BTW: This is the first time for me on this forum, and a first post obviously, so PMing would not work .. if this talk would be better in another thread, feel free to move, or resort to PM if this is off-topic alltogether. Then again if the 'killing the ego' idea is central to Sedona, perhaps this talk is on-topic after all - I apologize for not bothering to find out much of Sedona now. And thanks for the great fora & site!