I can't really add much to what others have said, only a couple of thoughts from one who has never been a JW...
I’m sure he and my DUB wife will likely mischaracterize it as an attack on GOD; anything said against the TOWER is always an attack on GOD.
When my JW friend and I got into a discussion about Christian persecution, they indicated that JW's were the most persecuted people for their religion (I guess trying to prove they had the truth through their persecution). I said, "JW's aren't the only ones that have been persecuted, almost every Christian sect/denomination has somewhere in their history been persecuted, some more than others, and some certainly more than the JWs"... this history goes back 2,000 years... I then sited several historical incidences, which of course they never heard of. So, does this prove that all these sects have the 'truth' since they were attacked, or "God" was attacked?
One other thing, my JW friend and I always get into biblical discussion (until they get frustrated and won't speak to me for a couple of weeks). One time, when they were trying to prove some ridiculous JW belief from the scriptures, I just said "You know, if I had to pick certain seemingly contridictory scriptures, I would only use the ones that came from Christ... I would discount the others... because He was our example, one we were to follow and imitate, so as simple as it seems, I do ask my self "what would Christ do"? He wouldn't shun, but would visit the sick and always uplift people by showing unconditional love.... between Peter, Paul and Jesus, I'd take Jesus and what he said over the other two any day of the week".... Well, my friend got huffy...shut up... and didn't speak to me for a couple of weeks.
Bottom line ... your example to your son seems to be more Christ-like than Tower-like ... hopefully he will recognize it for it's true value.