I've only had one bad encounter with a CM, but not at an attraction or anything.
It was durring Spectro Magic one evening, and my brother-in-law and I were squished into the back of the crowd with her daughter's stroller infront of us. We were standing there for a couple of minutes, when a cast member told us to 'not park the stroller on the sidewalk' (we were on Main Street). But the thing was, the stroller wasn't even on the sidewalk. My brother and I were just standing behind the stroller on the street, trying to view the parade. After telling him we weren't on the sidewalk, the CM repeated what he said, so now we had to wiggle out of what seemed like a can of sardines with a big honker of a stroller (it's hard, when there are hundreds of people squished infront and beside you, while even more people are walking right behind you). After obviously struggling to get out of the crowd, the CM yelled at us and motioned for us to leave, when my brother finally snapped and yelled back, "LET US GET OUT OF THE CROWD FIRST!" I could tell he didn't want to have to yell, but the CM was just being very rude to us when it was obvious we were trying to leave. Afterwards, the CM finally got quiet, and my brother and I finally left with a screaming five year old in the stroller.
Why the CM was so cranky, I don't know..maybe he was tired?