-You could also present the scriptures that talk about Michael, "one of the chief princes", the archangel and how there's no connection between him and Jesus (finish by reading Hebrews 13:8)
-Present to them the quote from The Finished Mystery book, where it states that Russell was still managing the Watchtower after he was dead.
-Also, read to them Matthew 28:19, and how Jesus mandated everyone be baptized in the name of the Father, Son, and the Holy Spirit, NOT the Holy Spirit-directed organization.
-Ask them to prove, using the Bible only, how Jesus picked the WT in 1919.
-Read to them Galatians 1:8, where it talks about how if anyone speaks of a different "good news", that that person should be cursed.
(I know most of the stuff above may make them "shut down", but it's worth a try)