With all those years I've tried to convert somebody into being a JW, I'd sure like to help get one out.
I'd want to explain why they are wrong, especially to my family. But, that's risky because I don't want to be shunned by them. I have helped point relatives who have "fallen away" to resources. In some cases, they still feel that it's right, they just don't go back. I think that's the right place where they can be helped and I try to push them in the right direction.
I don't approach members of my family who are still in. I only defend my position when they try to get me to come back. Strangers who are JWs, I have no problem with challenging them. And I think it's worth it. Many of us here wouldn't be here if somebody didn't plant those doubts.
As for what to show them. I've read enough about 1914 that I could speak on it. There's plenty more I could speak of, such as things from Franz's book. But, there's not a lot I could speak of from it. It takes reading the book to get the jist of it. So much stuff from the early publications is considered "old light" and JWs will ignore it as such. But when you put it all together to form a coherent record of how it all changed over time, it becomes more than "old light". It demonstrates just how much guesswork is involved in a religion that is supposed to be God's channel. And there's even more stuff in Franz's book that there's no way for me to prove. Like I can't prove some conversation Franz had or that some copy of an internal document wasn't forged. But much of the things from say, Carl Jonson's books can be shown from independent references.