Responsibilities of instructors to students when teaching controversial subjects
If the students are being assessed by you, some (most?) will start to tell you what you want to hear in order to get the highest grade. This is rarely what we as educators want in our students. We want to build within them critical thinking skills.

Controversial issues are common in some fields. For example, one of the subjects I teach is Business Ethics and I have clear beliefs and values in this area. Is it OK for me to focus on the arguments in favor of my view and discount competing arguments? No, it is not.

Can I tell my students my opinion? Opinions differ on this but I believe it is OK, as long as it is done very carefully with LOTS of evidence that my opinion is wrong. Again, students must be taught to think for themselves, including how to critically evaluate what they consider right and wrong. If I just make my points then it is not education, it is indoctrination and that is not what higher ed is about.

As far as social norms, I would say that if you are trying to get your students to 'believe' anything, then you are doing it wrong. If you are trying to get them to think critically, then you are doing it right. If the students feel they must agree with what you say, you are doing something wrong. If they feel like they are getting balanced information and a class ends up with many different opinions, then you are doing something right. If everyone is thinking the same, then nobody is thinking...and that's not good for anyone.