I believe that with playful competition, comes peace. During the Olympics, you don't hear news about bombing, or counties trying to invade other countries. You hear news about the sports. Having so many different ethnics in the same place allows for better understanding of others who are different from one another.
I strongly disagree that playful competition will bring peace. During the 2012 Olympics in London, there was an explosive device found three miles away from the Olympic Park and inside one of the Games training venues. London also had ground-based air defence systems despite protests within London. On a more recent note look at what happened during the 2014 Fifa World Cup. After the Brazil-Colombia game Brazilians began to threaten Colombians stating that they would "remove the head of Juan Zuniga". Threats were then returned Colombians stating that if one of their players were to be touched that they would slaughter the whole Brazilian team.
Your argument about having many different ethnics in the same place for better understanding of one another is more of an opinion. With that I leave you this: look at America. America as a country consists of many different ethnics cultures, beliefs, etc. Saying that putting people of different backgrounds in one place for better understands won't help. There are to many nationalist, and people go over board with many different situations including sports. In America alone we can't even have peace with high school sports.