The simpler, logically consistent solution would be that the child’s citizenship is only granted if the parents are citizens. (Or at least if parents are not illegal immigrants). Then when you deport the parents, you can legally deport the child too. It still is not a pleasant situation, there is no ideal solution here, except he should have never been let in at all, but once he is, these seem the only choices
Citizenship by blood creates its own problems. I am eligible for Polish citizenship if I choose to pursue it based on where my ancestors lived. I have never been to Poland, don't speak the language, and don't really know that much about the culture or feel any loyalty or even much affinity to Poland. On the other hand, let's say that someone is born in Poland to immigrant parents. Culturally they are entirely Polish - they lived their whole life there, speak the language, were educated by the Polish school system and consider themselves entirely Polish - they've never lived anywhere else. Yet they would not have the same ability to become a citizen that I have. If I got Polish citizenship, I'd just take whatever benefits I could from it and contribute nothing to Poland. How is it logical that I could be a Polish citizen and this person couldn't be?
I think there has to be a reasonable solution that gives legal status to the guy who's been here for 20 years and is making a positive contribution to society, but doesn't allow someone to show up and exploit loopholes to stay forever.
I think a reasonable compromise would look something like this:
* Make it much easier for people to get temporary visas for the kinds of jobs where we need migrant workers.
* Provide a pathway to citizenship for people who have been in this country for a very long time and are contributing to society.
* Make it very difficult for people to come to the US without a visa - e.g. make people apply for asylum outside of the US. Stop issuing temporary protected status to huge blocks of migrants.
Unfortunately, political polarization has basically made it impossible for Congress to solve real problems.
The net result, of course, is identical to if they had all stayed home.