One of the largest evangelical college ministries in the U.S. has asked any staff members who support same-sex relationships to quit, a move critics call a purge and supporter laud as an affirmation of true Christianity. InterVarsity Christian Fellowship informed all staff about the policy over the summer after issuing a position paper based on their three years of study of sexuality that concluded sex should be reserved for marriage between a man and a woman. The organization’s leaders said employees are expected to “believe and behave” in accord with InterVarsity’s stand on sexuality, including not engaging in immoral sexual...