The question of immigration can be simplified to a trade off between freedom and security. It would be wonderful for everyone in the world to have the liberty of choosing where they live and under what type of government. On the other hand, you have situations like the recent terrorist attacks in Paris and around the world by foreigners. If you allow outsiders into your country they are more likely to have outside beliefs that damage what you have. If you stop them, you force human beings to live in nightmares as bad as the Holocaust (think present day North Korea or the sex slave trade in the Islamic State).
My solution: open the borders, arm everyone (so you can have regular people like the Americans in Paris shut down terror attacks), and put in place harsh Roman style retribution removing the incentive to use terror as a tactic.