Booing is not something invented and exclusive to third world countries or Brazil for that matter.
Hypocrisy much?
In any case, that fact that booing has happened in previous events I can accept, but that seems a false equivalence. I'm pointing out that to my knowledge, this is the first time it has happened with such vigour and insistence at a world wide sporting event. What is the point of the Olympics if not to overcome partisanship in the name of good sportsmanship? A lot of the Brazilian fans' behaviour seems to come from the worst of futbol hooliganism, which no-one could seriously defend, and their booing of Argentinians in particular shows an unwillingness to rise above regional rivalries even for the Olympics.