They may well have been influenced by the pronouncements by various senior clerics, such as Sheikh Ahmed Ali Othman who is, according to the Al-Moheet Arab News Network, "supervisor of the Da'awa [Islamic Indoctrination] of the Egyptian Waqf [Islamic Holy places]", that pigs have descended from Jews and should, therefore, be exterminated.
It seems that there is some disagreement on the subject among Islamic scholars.
Sheikh Ali Abu Al-Hassan, head of the Fatwa Committee at Al-Azhar [Sunni Islamic university], said that the first view [that Allah turned Jews into pigs, monkeys and Satan-worshippers] is accurate, because when Allah punishes a group of people he punishes only them. When Allah grew angry with the nation of Moses, He turned them into pigs and monkeys as an extraordinary punishment... but they died out without leaving descendants.Presumably, that means that the pigs can be left alone, though not the Jews whose ancestors had not been turned into anything. How very confusing.