A Query for All Those Who Favor Amnesty

Why is it that your first line of defense is virtually always, "But you just CAN'T deport 12,000,000 people! Why, it would drain our Federal Government's resources to process that many people for deportation...."

Yet, at the same time, in the Bush-McCain-Kennedy Scamnesty bill that just met with a bad end in the Senate (but which threatens yet once again to rear its ugly head in July), there is a provision for the FedGov to process the very same 12,000,000 illegals for "Z" Visas!

Funny: It will exhaust the FedGov's resources to process them for deportation, but it will not tax its resources to process them for "Z" Visas?

Please explain your math and your logic?