That doesn't seem like a good argument for instituting a quarantine by blocking air travel but not ground travel. And why block everything including police, cargo and medivac flights for a quarantine?
Closing the El Paso airspace will reduce the number of people flying, but not stop it, lots of people will make the drive to Tucson or Albuquerque to catch a flight.
I could maybe see it if it was, say, LAX which is a major travel hub, but shutting down a small regional airport without also shutting down ground travel is "quarantine theater" rather than a real quarantine.
Tell me you've never been to west Texas.
...In Mexico, sure. The closest major US airport to El Paso is Albuquerque or Tucson, 4 hours each.
It's not labour camps, and not extermination camps, but rather places where people are 'concentrated' while the bureaucracy figures out where to move them next.
If anything it's really weird to present it as having to do with supposedly illicit immigration, since citizens and people with residence permits are vacuumed up as well.