Hamid Khan stood out among the Hispanics he marched alongside at a recent immigration protest. When one demonstrator asked Khan where he was from and the reply was Pakistan, the man asked, "'Then what are you doing here?'" Khan was surprised. "I said, 'Look, there are non-Latino groups who are also suffering under these laws,'" said Khan, 49, a commercial pilot and director of an advocacy group called the South Asian Network. Hispanics, the nation's largest immigrant group, are leading the movement to demand a path to citizenship for illegal immigrants and defeat legislation that would criminalize them. Khan's experience...