Just a quick note from someone who doesn't post here: I'm Brazilian and I have absolutely no problem with any of our neighbours. In fact, I think Argentina and Portugal are great countries (just to name a few of which some people claim to be hated by Brazilians).
I live too far from Rio so probably won't be at any of the ceremonies but I'd be very more than happy to cheer for any athlete, from any country, from any continent, of any religion, of any sexual orientation and so on. Unfortunately, I can't guarantee others will behave in a mature way. I find it appalling, ridiculous and very child