Let me give this another try.
The word to focus upon for the sake of answering your Q is not necessarily the word “relevant”. (I just happen to like accuracy and I’ve heard him say that so many times I just gave the accurate version)
The important word is BEST (predictor of behavior) as opposed to ONLY.
The way you have stated your misinterpretion of what he said, that important distinction has been eliminated. BEST is vastly different from ONLY.
Secondly, without context, the meaning can be skewed a variety of different ways.
As I said, this is not a general statement he is making about his profession. He is using it very specifically to those involved with and impacted by the destructive behavior of another.
He is saying it to illustrate the fact that, WITHOUT PROFESSIONAL INTERVENTION, this person’s behavior is extremely unlikely to change because people do what works for them (or what they are allowed to get away with). By the time an adult’s behavior is that dangerous to himself or others, nothing short of professional involvement is likely effective. We’re not talking about eliminating biting ones fingernails or losing 20 pounds. The context is more along the lines of abuse or addiction.
This is does not apply to disciplining or training young children as you tried to apply it. Children are much more malleable and good parenting, with proper discipline and boundaries, can do a lot to shape or change change behavior patterns. But left to their own devices they can develop all kinds of maladaptive behavior ending up as spoiled brats.
Without intervention, adults will usually continue in destructive (to others as well as themselves) behavior patterns.
That intervention could come in numerous different forms. An insightful book, a trip to jail, a religious experience, an illness resulting from the behavior, etc etc. Different things work for different people.
Absent that, people will continue in their behavior patterns.
Obviously, therapy or rehab can be another form of intervention which gives a person insight to overcome the behavior.
That statement he makes is usually found in the CONTEXT of trying to get people in denial out of denial.
In the case of abuse or addiction this is important in order to make it chrystal clear to those being placed in danger from another that the options are clear cut. Either intervention or get out of the situation before you end up dead or you and others are irrevocably harmed
That is the most frequent context for his statement. He ALWAYS frames it with the word BEST predictor, not only.
I have NEVER heard that statement from him WITHOUT the word BEST. it would be a foolish statement without it. I’m certain that checking transcripts of the shows will prove this.
It’s a very sensible statement meant to illustrate the truth that WITHOUT ANY MOTIVATION OR METHOD TO CHANGE, people will continue to do what they have done in the past. That is absolutely true.
And that’s precisely why the profession of Psychology exists. It can be a means to enable a motivated person to effect that change.
But, without the persons desire to change:
The BEST predictor of future behavior…....etc etc etc.