Racism is everywhere. If you can't deal with it in a game, you might as well stay in your room and never go out, because simply saying "Please stop, you're hurting me." will not mean anything to whoever is being racist towards you. They are JUST words. So are the phrases "Give me some tacos." or "Report for br huehue.". Being perfectly honest now, I've dealt with many foreigners in MANY games and what I find is that the majority of brazilians do not care about playing the game, they just want to have fun and don't care if it's at someone else's expense. Not trying to group all brazilians into that category, I do know some brazilians from DoTA/HoN that are actually god players and play to win. The other problem is that when you speak a language other then english in chat, people just presume that you don't speak it at all and typing afterwards in english wont convince them either. Just remember that this is a team game, and if you don't communicate with your team in a higher level game, you will lose because the other team will most likely be communicating.
tl;dr Ignore it or don`t play, racial slurs are just pixels on the screen, you`re not even hearing them.
Solution: Just speak english on team chat, the majority of players only speak english.