From a March, 2012 article:
Two UN experts in the fields of racism and minority issues have issued their own statement, stressing the need for greater attention to prevention and early action in response to the first warning signs of tensions caused by racism and discrimination that may lead to violence and conflict situation with serious violations of human rights.
“All relevant actors should pay attention to early warning signs, including the marginalization and social exclusion of specific groups of individuals; discriminatory legislation and policies; the persistence of racial prejudice and negative stereotypes; hate speech by public officials and the media; and violent attacks and harassment targeting ethnic groups,” said Mutuma Ruteere, the UN Special Rapporteur on contemporary forms of racism, racial discrimination, xenophobia and related intolerance.
Worth noting: the U.S. has systemic cases of all of those warning signs. I think it’s only because of the significantly greater visibility of today (thanks, Internet!) and their prominence in the world that we’ve had so few violent outbursts as a result, there. (The Gabrielle Giffords shooting is one such example)