Top Israeli defence and security former officials have written a damning letter in which they called Prime Minister Benjamin Netanyahu an “existential threat” to Israel and warned that his approach to the Gaza war is harming US interests. More than 30 Israeli establishment figures, including former military and intelligence chiefs, government ministers, academics and business executives, said they had “grave concerns” that Netanyahu’s visit to the United States could damage joint objectives, according to a recently disclosed letter. The letter, dated Tuesday and aired in Israeli media, was add…