This is certainly a graphic description of the violence of judgement, and the need to take radical steps to avoid it!  The narrative assumes that the Lord Jesus still had the little child in His arms (Mark 9:36-37), even though this discussion was hardly a benign nursery rhyme (interestingly many traditional English rhymes were cautionary and violent tales - because children needed to know the dangers of life).  The disciples were still in their spiritual nursery and needed to learn that they had a responsibility for the spiritual welfare of others – particularly those who were spiritually vulnerable.  Attitudes, teaching or behaviour that deflected others away from trusting Jesus, would not be tolerated.

The Greek word used for 'causes … to stumble' is skandalizo from which scandalise is derived.  In the days of sailing ships, to 'scandalise the sail' meant to stop the wind filling it and therefore slowing down the boat's progress and making it unsteerable.  Jesus was angry at people who prevented anybody coming to Him or stopping them making spiritual progress.  Today a 'scandal' is an embarrassment causing loss of face; losing something of the meaning.  Jesus' message was that His disciples must never hinder anybody from entering His kingdom.  Jesus rebuked the Pharisees for throwing away the keys to the kingdom (Matthew 23:13), calling them 'sons of hell' because they replaced gospel liberty for religious rules (Matthew 23:15).

Millstone punishment was not intended as an instruction or even suggestion of how to deal with such people.  It is a metaphor to indicate that God's punishment will be much more severe.  Likewise, amputation is not Jesus' recommended way to curb temptation.  Rather it is to show that whatever holds us back from Jesus is so spiritually dangerous that its removal must have top priority.  The style of the Jesus-people had to be radically different from pompous religionists that they were tempted to copy.  The Pharisees, and their like, were only interested in themselves.  They had no concern for those they despised (women, the bereaved, the chronic sick, beggars, and children etc) and assumed that God did not care either.  How wrong!  Jesus did care about them. He had Isaiah 61:1-3 as His commission, which He validated in Luke 4:18-19.  To go against that commission, would invalidate any claim to be a true disciple of Jesus.

The church is always at risk of being a club for the benefit of members.  But that is not Christ's ethos for His Body.  It may need radical surgery to deal with such an exclusive attitude, which leaves the outsider in the sin of unbelief or misleads them away from saving faith in Christ.  Romans 2:17-24 fleshes out the argument against religious hypocrisy which has no power to draw people to Jesus ... and gives us a lot to think about.