Prayer and Peace

Surely everyone wants peace. Surely any believer would believe that prayer is powerful. So who would be against the peace initiative of Pope Francis in a "together praying" event at the Vatican Gardens. So, let's just hold our peace and pray.
As a tourist, I have entered a Mosque and Buddhist Temples. I have prayed with Protestants, in spite of, some differences.
Many had invoked that it was all in keeping with Jesus' prayer before Ascension, John 17:21 "That they all may be ONE; as thou, Father, art in me, and I in thee, that they also may be ONE in US: that the world may believe that thou hast SENT ME."
The unity and oneness that Jesus desires is a unity with Him. It is "one in faith" that Jesus is the Messiah sent by God. It is being one with the Holy Trinity.
If what we really want is any kind of unity then we can simply submit to the United Nations or to the New World Order. Still, we do not because it is Truth that we ultimately desire communion with. We were created for the Truth... to find it and then, to accept or reject it.
For all the good intentions of the "peace and prayer" initiative and it's warm gesture to seek resolution to world problems, there will be an unsettling feeling that the Truth is being obscured.