To prove that they lied on the form, wouldn't they have to legally prove that he is a terrorist and go through the same legal process which you said will be avoided?
I believe it is 1) different venue for trial (administrative vs a criminal case) and possibly 2) different standard of proof, especially for non permanent residents.
(Not a lawyer nor an immigration expert on US law, though.)
(Not a lawyer nor an immigration expert on US law, though.)