I would propose this to be the right way to go about it. First, have a debate. Put everything on the table.

Start with whoever came in illegally at any point, all the way to those who came in recently, or those who eventually got naturalised. People need to be able to speak their mind on each of those categories without fear of being accused of racism, xenophobia etc.

Let the debate happen, and where ever people are comfortable drawing the line, let it be there. Anything is good as long as its people's informed choice.