My point in asking for this is that their are so many people out there that think they have the answers. The truth is, there is no right way to go about doing music. If theory has a part in that, great. If not, fine. To quote James Mercer (The Shins/Broken Bells) "whatever it is you do, just make sure it's good." I really believe in that statement, and while good can be subjective, I think people know "good" when they hear it in whatever way it applies to them. Some times we can be influenced by people who just have their own opinions, and their attempts to impose them on others can really mask their discomforts with what they are frustrated by. Sounds like your friend is doing what he wants, and is making good music. That is the key.
Thanks for sharing, and best of luck on your journey! :o
Douglas Showalter