Adulterous Christians aren’t trying to get the commandment against adultery removed from the bible. They aren’t trying to establish swinging as something to be celebrated.
Adulterous Christians are living as if that commandment isn't in the Bible. And to argue this point to many who practice adultery in the church (even among the leadership), they explain their actions away. So in essence, to use your statement, the church IS celebrating an adulterous lifestyle. Whether we remove the adultery commandment from the Bible or not, the fact of the matter remains we, the Church, are living as if it doesn't exist.