Earlier quoted context omitted.
Why is it insane?
Some woman who is 8 months pregnant comes to the US on a tourist visa and gives birth, then goes home with the baby. And then somehow that kid gets automatic US citizenship. And it applies even if the mother is not even legally allowed in the country. And you think that is not insane?
I think there would be a real problem with creating a class of people who live here their entire lives and aren't citizens. And then their children also live here and aren't citizens, and their grandchildren, etc.
It's not that birthright citizenship is ideal, but it prevents some other, bigger problems.