To those who can't understand why the chanting is a problem, it is fairly simple. Disney is a relaxing place for many of us, despite the crowds. The dull roar of the crowd is not a distracting thing, and it is expected at a crowded place. It is also easy to ignore because it is a constant "drone." When groups start chanting loudly, it destroys the atmosphere and also makes queue music, narration, and etc... almost impossible to hear. It is also very difficult to ignore anyone who is chanting. (Not impossible, but VERY difficult).
Since everyone has a right to an enjoyable vacation, it is important that no groups are allowed to chant because it is very distracting to everyone else. I have been around very rude cheerleader group as well as rude tour groups from various countries. (Band kids are mostly well-behaved, but maybe I'm biased since I'm a band director... lol). Anytime I take my band kids on a field trip, we always have a serious discussion about how the behavior of each individual reflects on the entire group, either negatively or positively. It's just a fact of life. If my students were chanting something and destroying the atmosphere for other guests trying to enjoy their vacation, I would want to know immediately, and I would expect my chaperones to stop it immediately (unless I was there to stop it). A theme park is simply not an appropriate place to do chants. That's really not debatable. Sorry. A sporting event is a much more appropriate venue for chanting, and most people actually expect and enjoy joining in or trying to out-chant the other team's fans. Again, it doesn't matter who is doing the chanting (unless it is an official part of a show or something...), it is wrong.
I mean, obviously there might be exceptions at some point, but in general, it is very annoying, especially in a queue when everyone is so close together.