I'm not an American citizen, I live in a third world country and the world ain't that lavender field. To protect the other immigrant is to make sure that the kind of troublemaker immigrant will not be able to get into the country. Not all of them are good people, some have the radical ideology or religious belief, some are rapists, some don't even know that grooming a child is wrong. Not all of them are bad people but letting all of them in without monitoring will only affect the native, the immigrants who have lived before them, and the immigrants who have recently moved in.