The past 24 hours provided a clear and painful picture of the momentous challenges American Jews face these days. The day began with news that President Trump has issued an executive order designed, the White House said, to fight anti-Semitism. Reporting on the order, The New York Times stressed that it will “effectively interpret Judaism as a race or nationality, not just a religion,” and that it “could be used to stifle free speech and legitimate opposition to Israel’s policies toward Palestinians in the name of fighting anti-Semitism.” Leftist NGOs echoed the same talking point, and a phalanx of pundits...