I think what John assumes is Immigration is indeed an unmitigated good and people just might mis-perceive the benefit.  What government should do is tweak and temper immigration policy to suit the times, based on evidence and foresight.  How many should come in?  What type (family class, economic, refugee), as they all have different needs and costs, but also different moral dimensions.  What is frightening is we speak as though immigration is only good, but bears no costs.  Ignore the realities of real peoples' concerns (unemployment, integration, strain on social services) and then they really will turn to a hard-core populist, like a Trump, to deal with their concerns.