Imagine being 18 and suddenly discovering you have to prove the citizenship status of a parent you've never met or else you'll be deported to a country you've never been to and who's language you don't speak
Imagine a country extending citizenship to a whole group of people for no reason other than the location of their birth, and then allowing said people to access the benefits of citizenship, including the ability to receive welfare benefits, vote, and run for office.
There is no problem having mechanisms in place for edge cases where the child has been abandoned, parents both dead and so-on.
i dont agree with the person you are responding to, but theres a difference between not being a citizen and being deported.