Why not a Crusade?
Our commission is to save sinners, every faith knows that. Every denomination has an idea how to work and live that commission. The Body of Christ is made up of believers. People who were sinners and are now saved by the Grace of our Father in heaven. The Father of us all saved our eternal souls by sending His Son down here to earth to pay the price for our freedom. Christ paid a price that He did not owe, we had a debit that we could not pay.
There are Crusades to save the lost. There are free Christian concerts and their goals (or their mission) is to win souls. There is nothing going on to unite the Body of Christ together for the sole purpose of giving Our Father the Praise and Worship do Him. That is why the Gathering of HIS body came to be.
Many see this calling to unite the Body of Christ, (with out trying to take or call the people of God out from their Churches and Fellowships their faiths and their denominations.) At the same time, this idea to unite, is very new to many people.
Some Pastors and Ministers resist supporting this idea because some see it as a way to pull at their flock, and as good shepherds they want to protect their sheep from "wolves in sheep clothing."
The Gathering Of HIS Body is to edify the Church, to lift up the Church's, to lift up the Body of Christ, not to tear it apart or bring division in any way.