I specifically and purposely used the word "confront" in the context that if I were in a situation where I know that the instructor were to pencil whip a student through a class.
When an instructor does that, he or she had lost all the respects dued to the position.
In the context of both the OP and your debate with instructors, the discussion is involving a dive master
candidate. A DMC is in the process of learning how to evaluate student divers, and as such is not ever in a position to know that an instructor is "pencil whipping" someone through the OW course.
As such "confrontations" are inappropriate and counter productive to the OW students, the DM student(s), and the instructor.
Further more, while DM level divers are professionals, (as opposed to candidates, who are not) and deserve all the respect and rights deserving of the title "dive professional", from non pros and fellow pros alike, I am not aware of any agency that, in the context of educating students, ranks a DM at the same level as an instructor. It would be better if the DM understood that they may not have the same toolbox as the instructor when it comes to evaluating students, and approach the instructor in a manner that would invite a conversation, as opposed to a confrontation.
Should a DM or DMC bring concerns and observations to the instructor? Absolutely, that is one of their functions in class.
Should an instructor listen to those concerns and observations? Absolutely, that is why a DM is there.
Should an instructor solicit advice and assistance from the DM? I should think the fact that the DM is present answers this in the affirmitive.
Should the instructor heed said advice? That depends on the situation, including but not limited to whether the DM was in a better position to observe or communicate with the student(s) in question, and whether the DM is making sound advice and is competent in the discharge of their position.
Should the DM confront the instructor? Depends on the size of the DM's ego, I suppose.
YMMV