I use the following whenever i ecounter a JW, to stop their THought Stopping: This would be said after exposing some facts to them about the ugly WT history).
If the JW, is well educated I try to rekindle their Educationalistic Ego.. Like. You are an educated person. Why dont you use your critical thinking to think this over.
Touch their free will criteria. Why dont you use your god given free will to make some research about this. Even the Bible warns us not o beleive everyone and anything.
If you value the word TRUTH, why dont you do some truthful research about this.