Just playing devils advocate here- both groups are wrong in the countries that they are visiting- neither group is 'doing their homework', but I have never seen adult tour groups cause much of a stink in WDW as far as chanting, etc. goes. Conversely, I've seen LOTS of adult Americans overseas really screw up with behavior. Is it loud? Not always, but most of it is best classified as arrogant or disrespectful like what women wear in churches when touring, cathedrals etc., talking loudly in the Sistine Chapel, etc. When they get 'shooshed' they get really angry too and ALL are warned beforehand. Many folks in 'Merica seem to think the rules don't apply to them. Not all, but lots do.
I really think it's more the age of the offenders than a strictly cultural thing- Pop Warner Football kids, Cheerleader tourneys, etc. are just as bad noise-wise and behaviorally as any foreign group.