Because he says it would be rhen be safe to give legal status to some illegals already here.
That’s amnesty.
I'm thinking of people who have actually been targeted with death for opposing the narcotraficantes --- people like that police chief down in, I think it was, San Pedro Sula who had his two lieutenants shot out from under him, and was told he and his family would be beheaded.
Also people who just have an innocent, non-culpable minor documentation problem.
This (almost) happened with our family, when we were adopting our son from Russia 17 years ago. I filled out a line improperly on one of the (many) documents I had to fill out, and we got a crisp, cold notification that the entire shebang was henceforward void and the adoption process terminated.
We were fortunate enough to find a faceless but not heartless apparatchik in DC who mercifully listened to our desperate pleas, rightly concluded that this was a paperwork glitch and not perjury or fraud, and let the adoption go through.
The idea of allowing entrance to people who are really in danger of death or inadvertently guilty of a Line 14b on page 97 hiccup, is well with the American tradition of rule of law.
As for the rest? Swift, humane transport and family reunion in their country of origin.