Sam2,
I’m not arguing how big a tzaddik Matisyahu is or isn’t. What I’m saying is that if you go by the theory that the music is a product of the person who composed or performed it, IF in fact a composer/performer leaves the fold, it’s likely that he was harboring such thoughts even before it was externally manifested.
There’s a book recently published, Through Music and Song-Music from a Torah Perspective by Rabbi Elysha Sandler which discusses the idea in a rational, sourced manner.
I personally have no idea at what level Matisyahu is, nor do I care to discuss it, but I will say that in my opinion, listening to that musical style is not good for the neshamah.