You mean these words of Jesus: "if he refuses to listen even to the church, treat him as you would a pagan or a tax collector"?
Was John the Baptist assumed into Heaven? If not, why not? Jesus said in Luke 7:28 I say unto you, Among them that are born of women there is none greater than John:
You seem to have purposely omitted the line that follows: "...yet the one who is least in the kingdom of God is greater than he."
The entire passage reads: "I tell you, among those born of women there is no one greater than John; yet the one who is least in the kingdom of God is greater than he." Certainly Christ's mother was "in the kingdom of God."