From The Internet Monk
The problem for many people is their desire to create a church of certainty more than a church of Jesus. On the other side of baptism and the Lord’s Table they want something that is never found in the pages of the New Testament. The churches of the New Testament, like Jesus’ parable, are a mixture of wheat and tares. Church discipline does not happen out at the perimeter, but near the center, where Paul understands the power of inclusion and exclusion will do the most good in making us like Jesus. Where the sharp edges of distinction need to be understood is by those who openly claim to be following Jesus in a relationship of community and accountability.
This distinction between perimeter and center is also shown in Luke 9:50 versus Luke 11:23; we often get things backwards.