That seems to be the general concern of the MMA fanbase. From a letter to the Sunday Junkie: 

This is one of the most anticipated rematches in UFC history but could come at a terrible cost. With all the trash Sonnen has said about Brazil, the Brazilians hate him so much that one of Yushin Okami’s Brazilian sponsors threatened to take away its sponsorship if Sonnen went Brazil to support Okami. Sonnen has gotten numerous threats due to what he has said. So just think what will happen if Brazil’s No. 1 enemy walked into their house and took down their hero. What if he gets mobbed on his way to or from the cage? How does that make the UFC look? Is the reward of breaking attendance records worth risking fighter safety/life?

It’s a general misconception that all lands south of the US / Mexico border are Mad Max style battlegrounds where one wrong step will result in getting stabbed in the eye. We joke about it all the time because what can we say, we’re scared of Others and making vaguely racist jokes about societies we don’t understand makes us feel better about ourselves. Plus the Mad Max thing is at least 30% truthish.

Does the UFC share the same fear of Brazilians? Well, maybe a fear of soccer hooligans, but overall Dana White says everyone needs to chillax a little:

“I think Brazil is getting a bad rap. To be honest with you, the first few times that I went to Brazil I was very nervous and thought, ‘oh my God,’ this and that. I’ve been to Brazil many times and Brazil as a country and Brazilians as a people are getting a bad rap. Brazil isn’t as dangerous and as scary and as crazy as everybody thinks it is. I mean sure, there has been some bad things that have happened down there in the past. Bad things happen everywhere, you know? We can say the same thing in Detroit, we can say the same thing in New York, we can say the same thing in a lot of cities across the United States. Yes, he (Sonnen) has said a lot of stuff about Brazilians and that country and lots of people are going to tune in and show up to see Anderson Silva kick his ass because that is what the Brazilians want. I don’t think that it’s at a point where, you now, people down there want to hurt Chael Sonnen, you know what I mean? They are going to show up, watch a sporting event and they are going to look for their countrymen and their hero and the best fighter ever to come out of Brazil or any other country around the world to win that night against Chael.”