Actually, the right to privacy has nothing to do with whether a law is just or unjust. I think we'll see an element of that creep into the law as they very concept of privacy erodes. But the basic idea behind privacy in the Fourth Amendment search-and-seizure context is that police ought to be subject to oversight (by the courts) so that they don't become a menace.

Incidentally, the problem with search-and-seizure jurisprudence is that every time the Supreme Court hears a case on the subject the defendant IS guilty--the debate is over whether the evidence of guilt is admissible in court. That makes it hard for the Court to turn a blind eye so they tend to expand the law in favor of the police every time they get a new case. The alternative is to free a known criminal. It takes guts to hold police to a principle when the immediate result is to free a criminal.