When it became obvious that they had appointed themselves. After reading COC I did an intense amount of research about the begining of the Watchtower Society. I researched not only Russell's contributions, but those of his close associates, John H. Paton and Nelson Barbour. The single thing that disqualified the WTS and identified them as frauds was their claim to be God's only prophet on earth. What genuine prophet of God would have a 100% failure rate for every prediction they ever made for over a century? Yes, they are a prophet, but unfortunately for them, they are the very ones that Jesus warned us of. Deut 18.
FWFranz