When I've worked with mentally ill people--and I believe that David Berg was mentally ill as well as a criminal sociopath--I've noticed that no matter how disorganized, confused, deluded, manipulative or dishonest the individual appears to be, there is a truth at the core of what the person is trying to communicate.
Truth cannot always be reasonably established by citing facts. There are systems of knowledge that are neither legalistic or scientific. Spirituality, imho, is one of those knowledge systems that has its own rules for knowing truth. Sprituality has several definitions; it is being used here to mean that which is concerned with the incorporeal, literally, "the breath."
What I mean by "incorporeal" is ideas, values, beliefs, aspirations. One's spirituality (as opposed to religiosity) is highly personal and idiosyncratic, because it is an expression of an individual's most deeply held conclusions about the meaning of life and death. These conclusions may not be entirely provable by some standards of knowing, such as the rational approach of scientific method.
One can accept values, beliefs, and hopes about the meaning of life and death through external sources such as church dogma or Bible-based teaching. As I'm using the term, spirituality expresses an idea, value, or belief that you've come to know for yourself as true through reflection on your lived experience. Therefore, spirituality may or may not have a direct relationship to formal religious teachings. Using this definition, we could say there is such a thing as an agnostic spirituality.
Because spirituality depends in some measure on the intellectual world of ideas & beliefs, it exists as part of the mind. The "mind" (a slippery concept I'll go into later) is fundamentally dependent on the breath & heartbeat, both of which are unconsciously controlled a physical apparatus in the brainstem. One of the Greek words for spirit used in the Second Convenant (NT) texts is "pneuma" or breath. Another word for spirit is "kardia" or heart.
Spirituality, then, is as much driven by unconscious desires and emotions of the mind as by conscious ideas and rational propositions (e.g., locial systems of belief). One's capacity to be spiritual in a physical body is based on aspiration (literally, exhaling and taking the next breath). While the brain stem controls the physical acts of aspiration and heartbeat, these bodily functions are associated in the higher brain (limbic system) with a set of affective states: longing & desire, loneliness & aversion. This particular assertion about affective states in the limbic system ("mind") associated with breath/apiration is a case where the science of neurochemistry supports a conclusion that meditation practitioners have accepted for centuries.
Now think about those affective states of longing & desire, loneliness & aversion. Aren't these states also often associated with human sexual impulses? I say "often" because sometimes an individual's sexual impulses get hard-wired in a funky way, such that the affective states of loneliness and longing, desire and aversion are over-ridden by the state of fear & aggression or a state of angry rejection.
Jung argued that the longing one feels for union (completion) with an ultimate Being ("as the hart pants after the water, so pants my heart after thee, O God") is essentially the same affective state one feels when longing/desiring intimacy with another human being. Genital sexual contact between human beings can be purely physical and extremely brutish, but when those human beings are open to emotional intimacy, that same gential sexual contact can and does arouse "higher" affective states completion and loss.
Completion and loss: breathe in, breathe out. Breath is very essence of an incarnate spirituality. Some religious thinkers (St. Augustine and Aristotle) teach that spirit is "mind" and exists independent of the flesh. This is the famous mind/body split for which Western philosophical tradition is so famous. The Gnostic heresy actually asserts that the "mind" (spirit) is trapped in and polluted by the flesh, which can only decay and die. Therefore, the flesh must be brought into submission. Sex (in any form) is verboten, because it further entraps the spirit/mind in the flesh.
Many Christians have no idea the extent to which their attitudes toward sex have been influenced by the Aristotlian philosophy (which influenced St. Paul & the writer of John's Gospel), Gnosticism, and a long tradition of Christian teaching about sexual chastity that began in the second century with Augustin of Hippo. None of the traditions that hold forth on the "evils of sex" are inconsistent with the Bible (particularly the epistles); on the other hand, you'd be hard pressed to find a whole lot in the teachings and life of Jesus (Gospels) that is devoted to any lengthy, indepth discussion about sex. Why is this?
As a teacher of spiritual truth, Jesus was more Jewish than Greek in his way of seeing the world. Therefore, he didn't have a lot of the Greek-influenced preoccupation with the spirit/flesh dichotomy. Jewish spiritual tradition views the flesh as sacred. Genital sex is a thing of the body; it cannot, in of itself be evil. How it is used in a relationship can be evil. ("That which is on the inside pollutes.") Mind and body are not separate, split-apart things in the Jewish spiritual tradition. That explains to me why Rabboni emerges bodily from the grave--the flesh and spirit are unified in life and transformed together in death.
Before I end this rambling reflection on a very complex topic, I'd like to add one other connection: There is a widely held tradition that interprets the experience of orgasm and emmision (particularly for males) as a "little death." If at a gut level one holds that sex is evil in and of itself, this "little death" a cause of despair--something to be avoided at all costs. However, orthodox Christian tradition has justified the natural need for sex (dangerous as it might be) as a means of reproducing humans and/or expressing emotional intimacy within the special dispensation of marriage. Because Berg rejected the notion that sex is evil in and of itself, he no longer needed the special dispensation of marriage to justify his inordinate preoccupation with sex. If you look at his sexual preoccupation existentially, Berg's mind/spirit was profoundly, irretrievably split off and confounded by the demands of his body. This is a definition of mental illness.