Don't call them "illegal immigrants". That's not right. A person cannot be illegal. Human beings cannot be illegal.
here's my "polite" response, which i used on the comment portion of a news article... feel free to use it:
Wow... you really read that as "the person himself/herself is illegal"?
Maybe english is your second language, but the term "illegal" is an adjective to the noun, "immigrant", thus modifying the person's immigrant status. If they said, "Garcia, an experienced lumberjack," then you would not criticize the writer for implying that Garcia is experienced at being a person, would you? Garcia is an immigrant. As an immigrant, her status as an immigrant is "undocumented", which is illegal.
my "not-so-polite" response, i don't recommend using...