According to the official watchtower interpretation of the parable of the faithful and discreet slave "On his return in Kingdom power in the year 1914, did Christ find a faithful and discreet slave class providing spiritual food, or information? - yes . . . " You can live forever in paradise earth 1982,1989 p. 193. So the watchtower claims that Jesus found a slave CLASS dispensing food in 1914. This is a bold lie about their own history.
1. Early on Russell taught that the slave was a class, but in 1896 he got "new light" that the slave was an individual. He continued teaching that the slave was an individual for the rest of his life. Russell died in 1916. Russell was a one man ruler and directed the society without regards to anyone else, so there was no CLASS dispensing food.
2. After Russells death the watchtower continued to teach that the slave was an individual until 1927 when they returned to the "old light" of a slave class.
3. Today's watchtower leaders have rewritten their own history and claim that there was a CLASS all along and ESPECIALLY in 1914. If you like I can post watchtower quotes proving everything above or you may already be in possession of them.
I think the witnesses you present this information to could attack the source of your quotes or you personally, So try to be as kind and loving as possible. Be sure to kindly tell them that Jesus is the way, the truth, and the life, not a organizaion.
Another tactic may be to claim that they got "new light" on the identity of the slave. There are two problems with this.
1. The idea that the slave is an individual was the "new light" replacing the previous "old light" of a salve CLASS. The watchtower has flipped flopped and returned to the "old light" of a slave class.
2. Even if it was acceptable for them to "flip flopp" on the identity of the slave, it does not give them the right to "re-write" and lie about there being a slave CLASS in 1914. This would be like the US presidency in which prior to 1992 we had a "Bush" presidency, then in 1992 we citizens got "new light" and had a "Clinton" presidency, then in the year 2000 we returned to the "old light" of a "Bush" presidency. However if we "rewrote" our history books and claimed that we had a "Bush" presidency all along and ESPECIALLY in the year 1995 was there a "Bush" presidency we would be LYING about our own history.
This lying about their own history proves that the modern day leaders of the watchtower are not members of the 144,000 of the book of Revelation. "And in their mouth was found no lie . . ." Revelaton 14:5 ASV