In most cases i think disney's management is just ignoring the situation. Those groups disturb the experience of other people. I feel disney just cares about their customer satisfaction. In most cases casts members are victims of disneys rules on pleasing their customers in every silly way, rather than thinking of safety. Maybe if the people complained more about those groups disney will consider taking some action.
I suspect you are fighting a windmill. Unless mass groups of American boycotted WDW, Disney has no incentive to really care if only a few people complain. You complain, they will at most send you some canned response about how much they care about you as a guest and how they will look into it - and that will be the end of it. Because at the end of the day they get a lot of money from the Brazilian tour groups. And more to Disney's perspective, Jan and Feb are low points in their schedule and since that is the prime time for the tour groups who do you think they will really care about?
They can afford to upset a few locals and even lose a few as future guests, Only when they see a real impact to their bottom line will they even really look into this or any other problem. That's just how corporation operate.