true, in the school i went to a student was scolded for saying "okay i guess" or something along those lines to a teacher because, to quote her, "teachers are not your friends". it's important to speak up your mind but in some situations it does more harm than good.
Honestly, if you're in an argument with someone are they end up resorting to insults... the best thing that can be done is to walk away. I know its cliche, but if you remain quiet and its in public then they end up being the one with egg on their face and people would probably sympathize with you. In short, sometimes the best revenge is non-resistance.
but for the teacher thing.. It really is true. I would not talk to a teacher about something that didn't pertain to class topics. Am I having a problem with bullying? I would have talked to a school counselor. Idle chatter about interests is one thing, but acting like your teachers or teacher's aides are your girlfriends always seems weird to me. And may, given certain circumstances, be a violation given the power imbalance between teacher and student.