Thanks, Andromeda - I was under the impression that you wanted to keep the discussion on-topic, so I'll just try to clarify what I said earlier.
You are clearly aware that the average JW, unlike yourself, has a very limited depth of biblical understanding, due in large part to the WT having discouraged deep bible study in favour of its own sad-excuse-for-biblical-scholarship publications.
My point is this: if you were to have your average JW look at Romans 14:5, they would be confounded, because on face value it places the onus on the *individual* as to the observance of one day over another. Your deeper understanding is way over their heads, and would be irrelevant to them.
When you know your "frenemy" and the thought processes they employ, you can confound them using their own logic.
fwiw, I am an atheist and have been for almost 20 years. But when I talk to my JW relatives, my ability to use their own "sword" against them has been very useful.