When is anti-Semitism not anti-Semitism? When it’s Jewish paranoia, is one answer. When it’s criticism of Israel, is another. The All-Party Parliamentary Enquiry into anti-Semitism published last week in the U.K. will be welcomed by many British Jews. The very fact that so high-level an enquiry was instituted in the first place confirms that the problem doesn’t exist only in their minds.

To call out anti-Semitism, unless blood has been spilt, is a hazardous enterprise in Britain. It draws the accusation of hypersensitivity....