Eon, its not that the Law of Isreal has/had no meaning, or that the acts which you listed which occured in the OT do not perhaps seem wrong by today's standards. Some of these acts were condoned by the Lord, and some were not - it doesn't matter how YOU view them, only how God does.
Edit ---> I'd also like to add that just because things are mentioned in the Bible (for example, polygamy), does not mean that they are condoned. They are simply being accurately recorded.
Edit ---> I'd also like to add that just because things are mentioned in the Bible (for example, polygamy), does not mean that they are condoned. They are simply being accurately recorded.