If I were you, I would tell them what I think about the falsehood of the Watchtower Society. Ask them questions about the past false prophecies, the absurdity of the issue on blood fractions, and so on. I don't know if you still believe in the Bible (I currently not, I am an agnostic now), but, if you still believe in it, you could show them how unscriptural is the Lord's Supper in the Watchtowerland. Indeed, this was one of the first issues that I began to reject when I noticed that the foundation of the doctrines of the Watchtower were created by an evil man, namely, Joseph Rutherford. For instance, I discovered that Rutherford published in the Watchtower that the holy spirit was taken away since 1918. I was shocked when I read it, and I realized that this guy was an apostate. I was also shocked when I read how Rutherford answered the Letter of Olin Moyle. Could this man have God's backing?