In my experience, we were taught to respond with something like: "We didn't come to your door looking for answers or for the truth!"
Given the magnitude of flaws one finds when researching the doctrines and the WTS own admission of not preaching the original good news, how totally presumptuous and disrespectful it is to invade the privacy of anothers home to try and tell them how wrong their beliefs are and then to arrogantly respond in this way when challenged