@maxdancona,
Is that the source of your offense?
If you called me an illegal gambler, an illegal drug user, or an illegal mattress tag tearer I would not be offended in the least.
The term "illegal immigrant" and "illegal alien" and accurate descriptors, and unlike "wetback," not intended to be offensive.
On the other hand the term "undocumented immigrant" is not an attempt to accurately describe someone who has entered a country in violation of its laws, but to make a political statement.
Frankly, I don't think people who break the law have much of a case for taking offense over how they, as criminals, are labelled, and from my experience most don't. It's the folks like you who seem to want to take offense for them.
Maybe we should consider the feelings of bank robbers and begin to call them "unsanctioned withdrawers."
I'm no fan of taxes, but the people who break our tax laws are "tax cheats" not "resistors of a confiscatory government."
Obviously illegal immigrants are much more that their crime, but so is a murderer. When discussing immigration and the impact of illegal immigration, these folks don't have much more of an identity than "illegal immigrant." It's kind of like when I get called a "rich guy" in discussions centered on economics and taxation. Should I be taking offense because those who use the term either don't appreciate or won't acknowledge all of the other things I am?