Your client has a valid deduction that he is not using, so I'm not sure if I would be comfortable with signing that return because the perjury statement says that to the best of your knowledge the return is "true, correct, and complete".  I could be wrong, but intentionally omitting a valid deduction doesn't seem to be a "complete" tax return.

In prior years, I would have definitely told the client they are an idiot and to take the deduction.  With all of the stuff that has been happening this year in regards to undocumented aliens ... I'm not sure how I would respond to the client.