50 "Do not stop him," Jesus said, "for whoever is not against you is for you."
Before the Reformation, the Christian world was nearly all "Catholic" in their beliefs and practices. Even today, the Catholic Church is the glue which holds Christianity together as the largest body (by far) of Christian believers. We were given the Deposit of Faith and Institution of the Church directly from Jesus Himself following His Resurrection from the dead. We don't understand all that we do (and so we have "mysteries") but we do as He instructed because He instructed us to do so for the sake of His Kingdom. We believe we are called to eternal life in Jesus and He gave us the Sacraments and His very Body and Blood as food for the journey.
Those who are outside of our communion and yet preach in the name of Jesus are not our enemies. If they are not our enemies, can they be enemies of God? Then I'll leave it to God to separate the wheat from the chaff in the time of his choosing and not presume to know who else has wedding invitations.