1. I think the first argument you need to consider is whether martial artists are obligated to teach anyone. I am not sure this is true. Western martial arts have become something of a commodity; I pay you to teach me kata and kata gets me belts and belts mean that I know something. I am not sure that relationship is a direct reflection of "learning" martial arts, nor a direct indication of the skill being transmitted from teacher to student. I do not believe the pay-for-performance model is an accurate transmission model for teaching martial arts. But, it does expose more people to martial arts to which they would otherwise be prohibited from seeing.
2. I think you need to decide on a metric of success by which to critique instruction, if you are going to argue for its institution. Dojo size? Gross income? Number of students? Number of black belts? Trophies? Number of students gone evil and through mortal combat defeated? I know some number of nice people who can talk my ear off about what I should be doing, but who have little ability to do what they say - they are truly invested in me learning the poor martial arts they practice. If they give me a syllabus, does that make the poor martial arts they teach better?
Not all martial artists are obligated to teach, certainly. But if someone is an instructor, they are teaching. The question then becomes doing a good job of it or a poor job. There is a lot of solid data on how the body and brain actually learn things. Should we ignore that for the sake of tradition, or should we incorporate it our skills as teachers (for those of us who teach)?
I'm not a fan of rank, or any of the straw men you've thrown out for metrics. How about time required for students to acquire particular skills? That's really the metric I look at when I'm teaching. What can I do to increase my students understanding and mastery of particular skills.
Yes, students have great responsibility, but I believe that if I am to respect myself as a teacher, I have to make the effort to be as good at that as I can be.