You don’t present any tangible proof that an African-American festival akin to St. Patrick’s Day would, in fact, incite more aggressive behavior by law enforcement. By proportion, black Americans may suffer more police brutality than white Americans, but that can be explained by the former’s relative deficit of wealth and concentration in highly populated areas. People in the Asian/Pacific Islander category are less likely to be killed by police than whites are. (https://www.pnas.org/content/pnas/116/34/16793.full.pdf)