how do you propose that the "delicate" infrastructure of the US can handle a clean doubling of population over the course of 1 year?
Not at all viable when you consider the cost of requisite social services to support such an initiative, which is one of the myriad reasons why no country has ever considered the option.
Germany's refugee crisis is a good example of the pros and cons.
How is it unfair?
Make no mistake, I'm also against completely open borders without deportation, for a variety of reasons. "Fuck you, got mine" is not one of those reasons.
Putting people in concentration camps and letting them die there (ICE) should not be legal. This does not even touch on whether deportations should be.
Your implication that they must stop patrolling the border lest they become literally Hitler, is patently absurd and an affront to people who suffered through the Holocaust.
Also I'm talking about deportations (and the associated camps, whatever you want to call them) is a separate issue from border control, in my opinion.
If you wouldn't mind reviewing https://news.ycombinator.com/newsguidelines.html and taking the spirit of this site to heart when posting here, we'd appreciate it.