I would say if they're running class and you find yourself having jumped into said class, you invariably show respect to your teachers. There is still a lot to learn. One needn't go out of their way to attend that class if they don't feel inclined, but it has happened where I'm literally at an academy, see who's teaching, may be in such predicament you propose, and decide it's better to train than to not train. The love for jiu-jitsu overshadows my personal feelings toward a single person. To answer your question, I can still respect them as a black belt, because our relationship notwithstanding, they've still put in the time and taken the beatings necessary to reach that point. Their game is still legit. Will I hang out with them before or after? Odds are....low. I don't believe it's right however to outwardly show any form of disrespect within the confines of an academy. From the moment we enter the academy to the moment we leave, the student is bound by duty to at least be a pleasant person. Though you'd hope for this 24/7. At least in the academy however, I can respect their accomplishment, I can respect their mat space if they are the one's teaching class, but no one is holding a gun to my head to be in the same building as that person or be on their mat space if my personal feelings towards them are overwhelmingly glaring over anything else. Bottom line, if we as students take the time to show up to their class, take the time to suit up in a gi or rash guard or whatever, we owe it to at least ourSELVES to be all about the jiu jitsu over our lack of respect for who is teaching. Pick up what you can. At the end of the day, we have a choice over whether or not we show up to that mat space on that given day.
On the internet, it's easy. We don't have to follow and/or friend them.