"Who are you to decide that immigration is the litmus test for whether someone is a libertarian?"
I'm a libertarian who thinks immigration is a litmus test for whether someone is a libertarian...
Look, my time in the libertarian movement leads me to believe that there are basically two major groups of people who call themselves libertarians:
People who want to secure a right to be left alone for themselves and their tribe, and
People who want to secure a right to be left alone for everyone.
In my experience, a lot of libertarians want to ignore this distinction. I think that's a mistake. I think these are two distinct philosophies and should be understood as such, both inside and outside the libertarian movement.
It's the reason the Rockwell/LvMI crowd is trying to take over the Libertarian Party and it's one of the main reasons so many of my non-libertarian friends tell me they've had bad experiences with libertarians in the past.
Immigration cuts right to the heart of that distinction, because it's an issue that revolves around the state acting against people who are almost by definition outside the "self and tribe" conception of liberty espoused by that first group I spoke of.
To the latter group of self-described libertarians, ICE agents tearing children away from their mothers is exactly the kind of evil that compels us to espouse liberty in the first place. To the former group, it's a peripheral issue.
That "do immigrants have rights" divides libertarians so virulently is, to me, exactly why it's a useful litmus test.
It should be the easiest issue in the world for a libertarian to say "no, the government cannot project violence against these people," yet here we are.