Less than a month before Donald Trump returns to office, two of his most ardent allies have plunged into a fierce online debate over immigration, specifically the government’s visa program that allows American companies to hire so-called “highly skilled” foreign workers. The clash started on Monday with Laura Loomer, the far-right social media character known for her virulent racism, condemning Trump’s decision to name Sriram Krishnan, a tech investor who was born in India, as a senior adviser on artificial intelligence.