Its not about punishing someone who had nothing to do with breaking the law... it has everything to do with removing future incentives for the parents to break the law.
This whole path to citizenship is stupid.
If you polled all the latin-americans on this issue, very few would want become us citizens. They want to work, earn money and mail it home. They would want o stay Mexicans, not Americans.
And THAT is the most succinct way to put it.
No one wants to be "mean" to somebody who's only memory is growing up in the U.S.
But they are simply pawns of those who want to use them for their own power - because they know that if they are amnestied, the rest of the family then gets brought in legally as happened as a result of the '86 Amnesty.
Within one generation you have entire Mexican villages living in a few houses on the same block in Los Angeles. And all screaming for more freebies from the Gringos.