Rory has an extremely important post over on his blog; the more I think about it, the more important I believe it is.
Whatever name you give to your practice (martial art, combat sport, self-defense, combatives, whatever), you are ultimately responsible for your own training.
Every teacher I've ever had who was worth a damn (and this applies outside of a martial arts context as well) was not only comfortable with being challenged, but was happy to be. They practically expected it.
Some of my favorite students are the ones who are always asking questions.* It shows that they are paying attention.
Don't surrender your right to think to anyone.
* For some reason, women seem far more willing to ask questions and challenge assertions that men do. I don't know if that's something about our culture, or about the kind of women who are attracted to combat sport, but some of the most challenging and thought provoking questions I've gotten have come from women. These questions (and again, this is cultural) are almost inevitably followed by apologies.