Poland’s Prime Minister Mateusz Morawiecki has told Volodymyr Zelensky never to “insult Poles again” after the Ukrainian president suggested his neighbor was putting on a show over their disputes on grain exports. The Polish leader fired back at Zelensky after the Ukrainian leader offered a veiled criticism of Poland at the United Nations’ general assembly this week, saying the dispute was “political theater” and that “some of our friends in Europe” have “made a thriller from the grain.” On Friday, at a rally in Swidnik, Poland, Morawiecki hit back. “I want to tell President Zelensky never to insult Poles again,...