Many of them were born here, their parents' little anchors. Our own laws created that situation. Now they might be afraid that when they get home, dad and/or mom won't be there...
Lets say you go on vacation...
and while you are gone a illegal alien family moves into your home and the pregnant wife gives birth in your living room.
you then come home...
do you let them stay? I mean .. heck.. the baby was BORN there in your living room! it would be racist to kick them out dont you think?