Interestingly enough, in my entire life I've only encountered two rude cast members at any theme parks. Unfortunately, they were both Disney parks. The first was about 10 years ago at the Bengal BBQ at Disneyland. The CM was just unpleasant and kept rolling her eyes because a member of my group couldn't make up their mind on what they wanted.
The second time was just a few years ago during E-Ride Nights at Magic Kingdom. My wife and I rode Space Mountain and we noticed that the ride was extremely rough sitting in the back. So the next time through, we asked the CM if we could sit in the front rocket, and we explained why. He showed no sympathy and said that we had to sit according to the row where he assigned us. Of course, that row ended up being for a back seat again. After trying to get his attention, we just moved to a row for the front seat. He LITERALLY yelled at us and demanded that we "get back to the row I assigned you to" (I absolutely swear this is no exaggeration. I was completely floored). I refused and once again explained why we didn't want to sit in the back (reiterating, as we had already explained, that the back was EXTREMELY uncomfortable). He then pointed to a bull pen like section by the loading area and said (again, I swear no exaggeration), "You wait right here! I will deal with you two in a minute!". We waited several minutes and finally another guest, who had witnessed the whole thing, offered to let us take their place in the front row. When we got to the end of the ride, I asked to speak to a manager. They made us wait quite a while before a manager arrived.
In both cases, I was offered compensation for our experience. And in both cases, I declined the offer, asking instead for an assurance that the CMs involved would be spoken to about this.
I've never had an experience approaching anything near either of these at Six Flags or other parks. However, my CM experiences at Disney are usually so great that I think the guest service reputation is certainly deserved (though I have to say that I have consistently found Knott's Berry Farm's employees to be superior to Disney's).
I'm sure there will be CMs out there who read this and will want to defend the CMs involved in these incidents. If you are a food server, I have no doubt it is irritating to wait for someone to make up his/her mind while trying to get through a crowd. Likewise, if you are an attraction host/hostess, I'm sure there is pressure to load guests quickly to keep the lines moving. But my take on it is this: There is NO excuse for rude behavior if "guest service" is part of your job responsibilities. You've been hired for this skill as well as others. If you're unable to deal with annoying (or even rude) guests in a professional way, then you're not performing your job.