It was billed as an "exchange of views." But Osaka Mayor Toru Hashimoto and the leader of an anti-Korean group nearly had an exchange of fisticuffs in a debate about hate speech.

Mr. Hashimoto is known for his outspokenness in public. Last year, he made headlines with his statement that comfort women, women coerced into performing sexual services for the Japanese military in World War II, were part of a “necessary system to maintain military discipline.” That comment drew widespread criticism and dealt a blow to his...