> PhDs on the other hand, regardless of the field, you've contributed something unique to the collective knowledge of humanity. Instant green card, it's even dumber to kick them out.

Depends on the field. I've met PhDs that are fantastic, and I've also met PhDs whose defining contribution to human knowledge over their entire lifetime was "I made this algorithm 2.3% faster in a specific tiny edge case that no one will ever care about."