Ok Christians, explain this to me?

I just heard a guy go on a rant in R&S about how the Old Testament was written for a Jewish audience by Jewish authors and doesn't apply today anymore. So Christians I ask this. WHy is the Old Testament to this day still printed in the bible? I'm just saying. If you don't want people dissecting your religion tooth and nail finding obscure things in Deuteronomy or Leviticus, then why keep them in there? Or are you going to give us permission to find any verse from the bible we want and make fun of you for it? The ball is in your court Christians. Your move.