From the beginning of the post: "One puzzling thing I notice about debating immigration is how certain people often are that strictly restricting immigration i

From the beginning of the post: "One puzzling thing I notice about debating immigration is how certain people often are that strictly restricting immigration is the right policy." He's talking about people who support significant controls on immigration, which is the current policy and the direction which some people want to move further in. Lee's not just addressing people who want to end immigration. The substantive argument he's making is that significant controls on immigration are bad.