They likewise apparently believe someone who has made a life here will just tear it all up and disappear to go to a land they don't even know, just because some flunkie says they have to. Gimme a break.
Now, if you are talking about some footloose kid who just crossed the border some months or a couple years ago, and who has no ties here, and can't find work all of a sudden, then sure, self-deportation will occur, as it has the last couple years. He will pack up and go home to his family until things here improve. But that's not the population we are discussing.