Columbia University officials said today they were investigating what happened Wednesday night when protesters stormed a stage where the founder of a conservative anti-immigration group was trying to deliver an address, an incident that ended in chairs being overturned, and charges that students violated the speaker’s freedom of speech. The incident, at Columbia’s Roone Arledge Auditorium, reflects the strong feelings surround the immigration debate in the United States. It erupted just minutes into a speech by Jim Gilchrist, the founder of the Minuteman Project, a self-appointed band of civilian border patrols that have focused mostly on preventing illegal immigration from...