One of the aspect that we, as faculty, focus on is the idea of ethics in the classroom. What is correct/not correct to present to students. Is it OK to relate to students at the expense of being unprofessional? All of these subjects matter, but I want to discuss inner-departmental ethics, especially dealing with graduate students and faculty.
I remember standing in front of a public speaking class in my second semester. I found myself teaching a portion that I did not believe was helpful in the field of public speaking. Not that it was a poor idea, I just thought there were ideas that should be emphasized more than the one that was on my script. Therefore I was a bit daunted, but I proceeded with the lecture with a fake smile on my face. To me, I found that this was a breach in ethical principles. Normally, I would of said, that the information is not accurate in my mind, but my faculty thinks so. However, I am a GTA, therefore I provide my opinions. I am not tenured, I did not create the lecture, I am not running the course. Therefore, I cannot tell my opinion or focus on the subject matter that I want. I must conform to the material
So there is the ethical breach. If we do not like a faculty members decision of what to teach, then we can do a few things. We can say that the information is complete garbage and explain why your method is most effective. However, it may come to bite you because the faculty may find out you have avoided the subject matter
Second, we could always teach the subject matter despite our opinions. Which is the safe way to go, but is it ethical? Should we automatically conform for the sake of conforming? Or should we break the barriers and try to teach something else. That as well tends to be an ethical breach, therefore it is difficult to decide what to teach.
If you have meetings about lectures beforehand, ethically speaking talking with the course director beforehand would be the most effective strategy. You haven't had to compensate for a lecture, but then again, you can provide your own opinions in theory. Some professors will not be as accepting as others, but the most ethical way of approaching the subject matter is at least trying to explain the nuances of the class. The professor may be stubborn, but the idea should be applied instead of not doing anything about the class.