"Nevertheless, it also upholds the concept of the "visible and invisible Church," meaning that all who are truly believers in every age belong to the holy Church invisible, while the United Methodist Church is a form of the Church visible, to which all believers should belong as it is the institution where worship in the name of Jesus is conducted and the sacraments are administered; nonetheless, there may be many unworthy members in the visible church."
Emphasis mine. There may be many? Surely the idea that there are any worthy people at all in the UMC is not official church doctrine is it? This is an especially odd statement to see coming from a denomination which puts such an emphasis on the unmerited grace of God through faith. Take it away Herman Melville:
"Heaven have mercy on us all - Presbyterians and Pagans alike - for we are all somehow dreadfully cracked about the head, and sadly need mending." -- Moby Dick, p. 73
If Melville doesn't help, perhaps Romans 1-4 could assist. Barth's commentary can drive the point home if needed.