Where's your evidence for the argument that restricting immigration is a bad thing? Figures, statistics, even anecdotes? In other arguments you have asked that other people provide evidence - now it's your turn.
Evidence only relates to proving positive propositions i.e. "what is".
When it comes to normative propositions "what ought to be" it is not necessary though it often involves providing evidence to prove some positive proposition.
For example:
(1) More employment is preferable to less employment.
(2) Minimum wage laws have negative employment effects.
(3) Minimum wage laws are undesirable
(2) is a positive proposition, that's where the evidence comes in. (1) can be neither proven nor disproven, it is not a factual statement, it's really a statement of value.
The most that can be said relating to normative arguments using the above example, is that: If (1), and (2) holds true, then (3). (3) only follows from (2) if you accept (1).
Of course we could abstract endlessly and keep asking why, but there comes a point where you must simply accept some normative proposition as being axiomatic. Let me illustrate:
Rape, murder, theft. Why are they wrong? Maybe because you believe that one person harming another is wrong, rape involves the harm of another and hence rape is wrong. But then you've just assumed that harming another is wrong. Why? You see we can keep on going forever. So there must come a point where you stop and simply accept a normative proposition as being axiomatic. So maybe you might end it there and say "harming another is wrong" and that is the axiom from which all your other policy conclusions, morals, etc. proceed from. Or maybe you just hold the view that rape is wrong and that is it.
My reasons for not liking most of the governmental restrictions on immigration is that i simply see no reason for why they ought to exist. And the reasons that have been commonly given for the existence, i find either completely false, misleading, deceptive or morally repugnant.