The left has to find a workable alternative that doesn't scream 'Open borders for everyone' before the usual dark nativist dynamics set in.

Nobody is screaming that. Nobody is demanding open borders. What I demand is respect for the right to asylum. Must I really remind you that it is a human right? That there is no doubt that the Syrians who make it to us come from one of the most horrible war zones of the world? They are entitled to refuge. Are you demanding the abolishment of this human right? Alterations to the UN Universal Declaration of Human Rights? The Geneva Conventions? Do explain, please. Are these the demands that you want the left to make?

epochepoque:

Also, even if it is received opinion that fences never work, fences will be built regardless and sometimes they do work (enough)

Yes, the Iron Curtain was fairly efficient. Do you propose to re-erect it? Is making this proposal what you expect from the left? You think the left should demand all that?