Hi EndofMysteries, "Jehovah's Witnesses are the only people who don't practice war and who preach worldwide!" is the most difficult thought-stopping platitude to overcome because a JW's cult persona believes that nothing else is relevant. Trying to disprove that thought-stopping platitude to a JW in cult mode is a fruitless endeavor. You need to ask JWs simple questions to hopefully empower their authentic persona to overcome their cult persona.
If a JW is trying to convince you that the Watchtower has the "Truth", by telling you that phrase, then ask, "What if I value critically thinking for myself more than preaching worldwide that the Watchtower has the "Truth"? What if I believe that the Watchtower is only a printing, distribution, and real estate holding corporation? Are you willing to confront your fears that I'm right by independently researching the Watchtower as much as you would research which new car to buy?"
If a JW is afraid of being labeled as an apostate, then the preceeding questions can be rephrased to appear like you are asking for help from another JW to provide an answer to a prospective "bible student" (recruit).
Peace be with you and everyone, who you love,
Robert