A J Mast for The New York TimesAlvin H. Rosenfeld is the author of an essay critical of liberal Jews that has generated heated debate. The American Jewish Committee, an ardent defender of Israel, is known for speaking out against anti-Semitism, but this conservative advocacy group has recently stirred up a bitter and emotional debate with a new target: liberal Jews. An essay the committee features on its Web site, ajc.org, titled “ ‘Progressive’ Jewish Thought and the New Anti-Semitism,” says a number of Jews, through their speaking and writing, are feeding a rise in virulent anti-Semitism by questioning...