Undermining God's Appointed Man

What is the sin of the so called 'super-apostles' in Corinth? Beyond the sin of teaching false doctrine, they are also guilty of undermining Paul's authority through creating doubt in the mind of the Corinthians concerning God's appointed man. Churches are still guilty of this sin at times - speaking sinfully about other pastors or churches in a way that tears down, rather than builds up the body of Christ.