How can we justify taking worldly ideas and concepts and Christianize them to be practiced in the church?

I agree that we shouldn't. Simply for the reason that we shouldn't be a friend the world (popularity). If you are a friend of the "world then, you are not a friend of God." It is a harsh concept for people- who want to be Christians to swallow, but it is the truth. IMHO I, even, sometimes waiver...