Yep, its bad. I'm brazilian and cant stand brazilians in online games, be it a MMO, Dota or FPS. Most of them cant even spell a word in english if theyre in a party/raid with the majority of people from another country. They spam "heuauhuhehua" and are just annoying.
My first time playing with them was in WoW, I tried to play in the brazilian server (Warsong Gulch) and couldnt stand it. So much hate and people flamming each other, not only what they call "gringos", but even other brazilians. Seems to me its the same thing in Dota, if you die once in a MM with brazilians or dont do what youre told prepare to hear a lot. Unfortunately I think this goes beyond the realm of games and most brazilians are just ignorant in general and lack proper education.
this happens all across SA