I believe that I am a customer when I go to a class, and the instructor is a service provider. It took me a long time to reach this point, but when I did, it certainly helped my confidence and self esteem when I went to class. I f you take this attitude, you shold feel it's your right to ask all the questions you have on the topic as long as you are not interfering with the other students taking the course. Try to get your friends who take classes to adopt this attitude, and you will find that you have a much better mind set to handle inappropriate comments from the instructor. I find that I can respond with, "I don't believe I understood your explanation. Could you please review it? A response of "no" is not an instructor's option.
I find that it's also useful to teach this attitude to students going to college, so they can feel less intimidated by professors. After all, they are just instructors that you have paid to teach you what they understand.