My only logical "fear" for immigrants isn't that some might be terrorists, it's that them simply -being- is causing violence both towards them and by them. Due entirely to xenophobic nationals and -some- immigrants NOT performing what should be their civil duty to conform to the country they now inhabit. You could argue nationals should have the civil duty to at least learn basic bilingualism to communicate. But that's a trite argument at least here in America, as some Americans act downright offended that they should know at least some Spanish.
And I have personal anecdote to add since I'm a citizen of the great state of Michigan home to the famous town of Dearborn, where it's entirely a Muslim community, and many of the adult Muslims living there can't speak much English, and in my own experience their children who went through the public school system translated for them.