President Donald Trump’s meeting Wednesday with South African President Cyril Ramaphosa began cordially — but when Ramaphosa protested against claims of “genocide,” Trump turned on a video. The video showed radical leader Julius Malema and other black political figures addressing rallies, chanting slogans such as “Kill the farmer!” and “Shoot to kill!” The video also showed threats to seize white-owned farmland, and a large memorial to murdered farmers featuring over a thousand crosses along a roadside. Ramaphosa had begun by avoiding the issue, saying instead that he wanted to focus on trade, investment, and efforts to promote peace around the...