Actually, a better analogy would be calling Illegal Aliens(the actual legal term) "undocumented immigrants". 

The bottom line is, it is a deliberate misuse of the language to try and affect political dialog.

I can think of a whole lot of words and phrases that have been deliberately 'redefined' to suit a political narrative. Here is a short list:

racism
gender
man
woman
socialism
fascism
hacked
sexual assault
privilege
the list goes on and on