Kashering the Material

In the previous post, the message was Torah-true but the one conveying it was not up to par.  What about the other way around, when the message isn't coming from Torah but the one conveying it is a fine, frum Jew?

Many of us wonder about various approaches to life's issues that are taken by those in the helping professions.  Often, these approaches are not coming from Torah, but they are adapted for a frum audience.  For example, frum authors like R' Zelig Pliskin study secular self-help sources and then present the material for frum audiences with relevant examples.  Does this "kasher" the material? Do we say, there is wisdom there and we can and should benefit from that wisdom?

Perhaps the truth and the benefit of the model depends on how it was come by.  By that I mean, did the person already have an approach that he or she used, and only afterward try to see how it fit with Torah sources? In other words, it wasn't Torah that informed their decision.

Or, were they not invested in any approach but looked to see what tools "out there" might be useful to a Yid in his avodas Hashem, middos improvement, and general life.

For the most part, I read and hear of frum people who have already invested in a non-Jewish approach who then try and show how it "fits" with Torah.