GENEVA—Britain and other countries drawing up legislation to regulate online content—including racist abuse—must avoid overly broad definitions and over-reliance on algorithms that might curb free speech, United Nations officials warned on Wednesday. Some 40 new laws on social media have been adopted worldwide in the last two years, including Vietnam’s 2019 cybersecurity law, in which the experts said had been used to delete posts and arrest those voicing critical opinions. “Virtually every country that has adopted laws relating to online content has jeopardized human rights in doing so,” Peggy Hicks, a senior official at the UN human rights office, told a news briefing. “This happens both because governments respond to public pressure by rushing in with simple solutions for complex problems; and because some governments see this legislation as a way to limit speech they dislike and even silence civil society or other critics,” she said. Hicks, asked to elaborate …