I could see “invite them to come back” to simply mean prioritizing those who have successfully learned english, held jobs, paid taxes (real estate, sales, payroll, etc...) raised families and contributed to American society over those who have not. When we implement our new system of legal immigration, we can say that if you have previously successfully lived in America you are bumped to the top of the list to come back.
I wouldn’t have a problem with that. It would be like having an employee who has done a great job for your company over the last 10 years and finding out they lied on their resume to get the job. You fire them and post the open position. The ex-employee applies for the job with an honest resume and is far more qualified than any of the other candidates (seeing as how he did a great job in the position for the past 10 years).
But that isn’t the red meat Trump threw out.
The other candidates thought this was a campaign, not a circus side show.