DNIPROPETROVSK, Ukraine — From his office atop the world’s biggest Jewish community center, Shmuel Kaminezki, the chief rabbi of this eastern Ukrainian city, has followed with dismay Russian claims that Ukraine is now in the hands of neo-Nazi extremists — and struggled to calm his panicked 85-year-old mother in New York. Raised in Russia and a regular viewer of Russian television, she “calls every day to ask, ‘Have the pogroms happened yet?' ” Rabbi Kaminezki said. He tells his mother that they have not, and that she should stop watching Russian TV. “It is a total lie,” he said. “Jews are...