The deportation policy is certainly NOT about racial profiling.  Local police stopping cars driven by people who look hispanic is racial profiling.  That's not a "deportation policy."  

And I agree that stopping someone simply because he "looks like an illegal alien" is unconstitutional.  There is no such "look," so such a stop could not be grounded even in reasonable suspicion.  

Speaking of stops based on reasonable suspicion (as opposed to probable cause):  If there's reasonable suspicion to believe someone has committed a crime, police have a right to make a "Terry" stop, or brief detention, during which which they can question the subject about who he is, where he lives, what he's doing, etc.  Terry v. Ohio.  Why should it be out of bounds to ask whether the person is here illegally?  What Constitutional provision does it violate?