After repeatedly suspending the Twitter accounts of groups associated with ISIS, CEO Dick Costolo revealed that he and his employees had been threatened by the brutal jihadist faction that has carried out and publicized beheadings of journalists and care workers. Costolo revealed the death threats during an interview with author and Aspen Institute president Walter Isaacson during a conversation at Vanity Fair’s New Establishment Summit. According to a post on Vanity Fair’s website Friday, Costolo said the threats for the “assassination” of both management and staff at the San Francisco-based company were shocking, saying, “that’s a jarring thing for anyone...