Ok, I am going out on a limb here. First, I do feel that the tour groups from any country should behave in a reasonable fashion, however, I also feel that we have to, to a degree, respect their culture as we expect them to respect ours. Having said that, we really don't have to look much further than ourselves for bad behavor. I somehow have a huge problem pointing fingers at any visitor to our country when our children behave horribly and some adults also.
Temper tantrums, screaming, yelling etc. are very prevalent in our country and tolerated by the parents of American children. Foul language, me, me attitudes are all a large part of the behavor of American Adults.
It is rather difficult to say, "oh those Brazilians are awful" when they are doing nothing more than having a good time and are totally unaware of our culture.
The American Cheerleaders are foul mouthed, loud, inconsiderate, and just plain spoiled rotten. It is not limited to the resorts and it is evident throughout the parks. They have no excuse, they know the culture.
I would far rather enjoy watching someone have a good time than watch a kid scream at the top of their lungs or throw a temper tantrum and have the AMERICAN parent look on like it was nothing and not a big deal, which, it probably is not to them, but, for someone trying to enjoy any attraction at any park it is not a fun thing.