Uh, oh.... Again, keeping in mind that I'm a rather shallow person and that I'm probably sticking my nose in where it doesn't belong...
I do believe I might have worded my response to a son of my own just a BIT differently... Maybe like so??
"Well, Son, I am very interested as to which Bible you've used to find these scriptures in. Personally, I prefer [X] version/translation. What is it about your bible [whatever translation] that you feel represents the meaning and spirit of the ancient Christians more accurately?" [leave it an OPEN question, WITHOUT a hint of sarcasm - I hope!!]
[Whatever the reply...] "Y'know [word whisker...], Son, I never thought about that. Just out of curiosity, what does your translation say about [uhm, having trouble picking a topic here - as I said, I'm no Bible scholar] - brotherly love?"
[Son's response]
"Well, that's enlightening! However, it's always been my understanding that the bible was written for ALL to understand. As Jesus said, "As you recieve freely, so also give freely..." [AGAIN, I'm NO bible scholar... You can probably come up with many more scriptures; the point/focus I'm driving at is this - any scriptures you can quote that state that the bible is freely open to all, without any SPECIAL interpreter or mediator other than Jesus himself - or something similar...]
[Son's response or dissent, asserting the need for the Watchtower Society to interpret the bible for mankind today...]
"Fascinating. But, Son, that worries me just a bit. What about all those Christians who lived before the Watchtower Society existed? [Perhaps briefly mention that Watchtower Society is only 130 years old; that they ALSO believed in many things that the current Watchtower now calls "part of Babylon the Great"...] Who interpreted the bible for them?"
[Son's response will be something to the effect that God's holy spirit interpreted for them among early Christians and down thru centuries.]
[This is where you will need to do some research. The Watchtower Society occasionally quotes early Christian authors; if you can find one who is quoted within Watchtower literature, whose early Christian writings included theological ideas that the Watchtower Society would consider 'apostate' if spoken of today, I'd quote him/them. When doing so, FIRST quote the portion that the Watchtower Society used in their - hopefully recent - publications, and then slip in the rest of that early Christian's beliefs...]
[Wouldn't hurt to then ask...] "What do you think of that, Son? What if this early Christian, who the Watchtower Society has quoted as an authority within their own literature, were to stand up in Bethel in front of the Governing Body and make these statements to them?? Do you think the Governing Body of the Watchtower Society would approve of this man's words?? What would they do with him if they didn't? Would they kindly allow him to continue "dwelling in the house of our Lord" [some such scripture...] as mentioned here in [X] scripture?? Would they listen to his spiritual wisdom? What has happened to present-day Jehovah's Witnesses who may have brought out such points to their Elders within the congregation? Have they met with approval, or did this become a cause for them to be 'shunned'?"
[Wait for son's response...]
"Well, Son, I can agree that God's organization on earth must be kept clean, but remember that we're discussing the thoughts of an early Christian who had accepted the fine sacrifice of Jesus' blood so as to become part of his heavenly 'bride'... [You might quote the scripture that describes the things that early Christians were to keep pure from - something to the effect that "We favor adding no further burden to you brothers, only this: that you keep yourselves clean from things (meat??) sacrificed to idols, and from men who lie with men, and from blood. These things we exhort you to, but nothing more..." HEAVILY paraphrased, and not too accurate, but you get the idea...]
"If this early Christian accepted Jesus' sacrifice and became part of his heavenly 'bride', then, according to the Watchtower Society's teachings, he must now be residing in heaven with Jesus as part of that 144,000 heavenly bride class, right? [I think you can see the potential openings here... ]
[Then discuss with your son the Godly qualities of love and forgiveness. Say something to the effect of...] "Wouldn't you agree, Son, that this fine, righteous early Christian had much wisdom to offer modern Christians? But you can see that many of his comments would have caused him to be ostracized by the Watchtower Society, wouldn't they? Do you think it's right for the Watchtower Society to harshly expel members who have stated such opinions, instead of showing Christian love and patience with them?" [Perhaps quote the scriptures that state that "God is love" - and more of that scripture than the Watchtower usually quotes! Also, someone onboard recently quoted the scripture about "If I speak in tongues, and perform great healing.... but do not have love... then I am but a sounding cymbol,... I am nothing..."]
[Others here will be much better equipped to advise you as to which topics to pick. If it were me, however, I'd pick topics that are somewhat 'iffy' - without a direct slap/confrontation - no references to pedophiles or military service at this point...]
[Maybe get started with an actual translation of the Greek scriptures, ESPECIALLY using a Watchtower translation - pick up an older version, if you can... That way, when your son quotes scriptures from the Watchtower bible, you can counter with quotes from THEIR translation from the original Greek... It will reduce the quantity of scriptures you can dispute, since even THAT version of the Watchtower 'direct' translation has been strongly slanted to THEIR interpretation, but there are enough discrepancies between their own translation and what they SAY it says that you might be able to rattle your son's confidence in the WTBTS' "divine infallibility" (which, of course, they'll deny any claim to...)
I don't know whether you're familiar with the Watchtower Society's mandated style of 'reasoning' with 'interested' ones, but in re-reading what I've written, I realize that I've picked up/replicated that style, to an extent. All those years suffering thru their Kingdom Ministry School are 'paying' off...
I suspect that replicating their STYLE of speech while using your more accurate information would help you to be much more effective in slipping ideas past the Watchtower Society's mind-control techniques, into your son's mind...
As before; hope this helps... Zid