I'm a bit puzzled as to how this is part of the Great Commission, or preaching the gospel.
I'm wondering what Paul would think about it. Oh, I do know what Paul would think about it:
What business is it of mine to judge those outside the church? Are you not to judge those inside?
1 Corinthians 5:12
It also seems to me that Jesus' approach with sinners was somewhat different than how these Pharis--um, preachers--are operating. In fact, I seem to recall he saved his venom for people who were doing the sort of things these preachers were doing.