I have only had one memorable negative interaction with a CM and it was maybe18 years ago. It was so negative I still remember it (and most days can't remember what I had for breakfast)!
It was "the perfect storm" of events. It was our last day and we had a lunch reservation at the Poly and were to get our transportation to the airport for our flight home at the hotel immediately after lunch. I try very hard to plan things well, leaving enough time so as not to be running like crazy people through the parks at critical times.
Well, we were on thunder mountain and it broke down. We were held on the ride for a long time, but when we got off thought we would still be able to exit the park and maybe even be able to make lunch. As we came out of the exit they had ropes up in anticipation of a parade that would start from the frontier end of the park. As we got to the cross walk there was not a parade in sight. The cast member (a man), told us we could not cross due to the parade starting. We tried to explain our situation and he would not listen at all.
It was crazy- one lady seated on the ground was looking at us like we were being rude, another was telling him to let us across, it was surreal, people actually started arguing.
We only had infrequent trips up to that point and didn't know our way around Disney very well. Now with more experience, I realize we could probably have headed back toward thunder mountain, use the walkway by the river, etc. but at the time had no idea, and he didn't take the time to explain the alternate route we could have walked.
I usually address people as sir or ma'am and said "sir, please let us across as at this point we are not only going to be charged for a meal we can not eat, but could miss our transportation to the airport". (Keep in mind this was 18 years ago, I'm not even sure we had a cell, I didn't know how to call the restaurant, and was getting panicky about not making it to the airport).
What followed was one of the craziest things ever. His response was to pull the rope up against my waist with a bit of a jerk and I thought my husband was going to deck the guy! Another cast member noticed what was going on, stepped in and escorted us across. And, I am assuming they might have had problems with this man in the past, because he gave us the mans name (which I failed to notice in the excitement) and told us to call customer service to report this.
I did call their customer service after we got home, and the lady on the phone confirmed that he not only should have let us cross, they were allowed to do this, but the issue with the rope was unacceptable. She actually asked me what I wanted in compensation. All I asked for, was if they could not charge us for the meal we didn't show up for and for someone to speak to this man about how to handle something like this in the future. She said she would credit our credit card and that they would talk to him.
Crazy experience, but since that time, I have never had anything except wonderful interactions with CM's, and by now we are 1-2 trips a year.