The decision of the British Labor Party Thursday to suspend its former leader, Jeremy Corbyn, over anti-Semitism is an astonishing development. It follows an official finding that party officials had failed to deal with anti-Semitism in the party and committed "unlawful acts of harassment and discrimination." When Mr. Corbyn reacted by blaming exaggerations by his political opponents, the party promptly suspended him. It is, at least from this side of the Atlantic, a breathtaking moment all...