"If the second part of the sentence doesn't apply to the first, then there is absolutely no point in even adding the second phrase sense it has no meaning except in the context of the sentence."
I think all of the first eight amendments have several clauses that are unrelated (e.g., the 5th Am talks about grand jury presentment, double jeopardy, takings and other matters that have nothing to do with one another). The way I see it, the 4th Am actually has two clauses that have something to do with one another (both have to do with searches by the government), but one has to do with the reasonableness of the search, while the second imposes a limit on the ability of the government issuing a warrant to protect the police from liability. I will grant you that if there is probable cause and specificity and a judge thus issues a warrant, it would be very difficult to argue that such ensuing search would not be reasonable, but that does not mean that the opposite is true (that a warrantless search is per se unreasonable).