On Monday, Harjap Singh Banghal got an unexpected call from the police, who warned him that he had become the target of far-right activist groups amid ongoing riots across the U.K. A renowned immigration lawyer whose offices in London and Birmingham regularly assist asylum seekers with their claims, Banghal’s work landed his name on a list—which includes up to 60 names of individual lawyers, law offices, immigration centers, and refugee shelters—being circulated on social media platforms with the phrase...