Christians have always struggled to view the whole of Scripture as authoritative in a practical sense, but it has become fashionable of late to deliberately argue that 21st century Christians should have a canon within a canon, that we modern, enlightened, scientifically-oriented believers have the wisdom to decide which Scriptures are relevant only for today and which are only for a by-gone more primitive era.
The problem with such a view is that the church hasn't left us with that option. All Scripture is authoritative and necessary for Christian ethics, for Christian life-- from law to prophetic pronouncement, from poetry to prose, from parable to narrative-- all of it is authoritative. Once we realize this, we are freed from the arrogance of suggesting that we know more than the ecclesiastical wisdom of the ages what God has and has not said, and we can spend our time reading, interpreting, struggling, and wrestling with the biblical narrative from Genesis to Revelation in all of its complexity.
To pick and choose what we believe is and is not the voice of God is to succumb to the temptation that the Bible tells us we have fallen prey to for centuries-- creating God after our image and our likeness. When we decide what is and is not "Scripture" we become divine authorities in our own eyes and God marches to our beating drums rather than the other way around.
Stanley Hauerwas says that the great thing about Christianity is that we don't get to make it up; we just get to receive it. It's enough of a struggle each and every day just receiving the Christian faith and the foundation of its Scripture for living; let's not add to our burden the ominous responsibility of deciding what in Scripture is the voice of God and what fails "in our own eyes." The Bible is very difficult and in some places even disturbing. The answer to such passages is to attempt to understand them in the whole of the biblical narrative, not simply to dismiss them. As I have said before, fundamentalists and progressives have one thing in common when it comes to biblical interpretation-- the former just ignore the difficult Scriptures, the latter simply dismiss them leaving the consistency and the coherence of their faith intact. I prefer a much messier hermeneutic because life is messy. Should it be a surprise that the biblical record is messy too?
So, let's not promote what will become an impoverished Christian faith by just dismissing the portions of the Bible we do not like. The Bible is not like a menu at a restaurant.
To use it in such a way is too easy.