You have some good reasoning. And even all the reasoning the WT gives in your quote is simply their own perspective. Like they say, 'What about all the improved understanding we have gotten over the years?' Yet, the supposed 'improvement' is nothing but their own opinion. But we are the only ones who see that.
More and more I see Matthew 7:6 ('not to throw your pearls before swine') as being the best response to them. I come to prefer to simply to throw the question back at them, or use some non-engagement type of response like, "I'm not the judge of those things" or "You'll have to show/tell me" or "That's something to think about" repeated over and over.
Most of them prefer the mind prison the WT has imposed upon them (yes, this past week's WT study on free will was so ironic!). And they are not likely to budge from it until it becomes uncomfortable to them personally.