Only one example should suffice to refute the notion that the bible doesn't need to be taken as a whole, that not all of Scripture is relevant or profitable anymore.

"All scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness: That the man of God may be perfect, thoroughly furnished unto all good works." (2 Ti 3:16-17).

That says it all.

And for all those who want to argue that in Pauls' times, "Scripture" was not the bible that we hold in our hands today, remember that you would have to stick with the Old Testament only then, and remember also that you would thereby deny the fact that whatever is written in the New Testament is inspired by God and thus God's inerrant word too.