Just pointing out that most on this thread have been quick to point out that their use of "Brazilian Tour Group" is because of the large tour groups from Brazil. They are equal opportunity haters of "Cheerleading Tour Groups", "Pop Warner Tour Groups", "Marching Band/Chorus Tour Groups", and any other group that travels in large numbers and interrupts their touring plans. If a large group of Franciscan Monks visited the parks, you can bet we'd hear complaints about the Monks.
Add to the fact that, as has been explained, most find traveling with their own teens to be (barely) tolerable, but they have no desire to spend a lot of time around groups of 20-80 highly unsupervised teens in a foreign country. I'm sure the Canadians were cursing myself and the parents of all the kids who went on the trips to Canada to study the architecture and cathedrals... and I can assure you that ds and his friends are the model of decorum and respectability when in the presence of adults who would not hesitate to stool them out... in a foreign country? Although I would like to think differently, probably not so much at certain times.