A South Korean court on Thursday sentenced the leader of an online sexual blackmail ring to 40 years in prison, the Yonhap news agency reported.Cho Ju-bin, 24, was found guilty of running an online network that blackmailed at least 74 women, including 16 teenagers, into what authorities called “virtual enslavement” by forcing them to send increasingly degrading and sometimes violent sexual imagery of themselves between May 2019 and February 2020.The Seoul Central District Court sentenced Cho…