I'm not a JW, but if I were, it would come down to this:
On one side of the scales, we have plain and simple, black and white, clear and direct commands regarding the sanctity of the gift of life and the severe penalty for unjustly depriving another human being of that gift.
Only something of equal weight can balance those scales.
From Uzzah to King Saul, the Bible is full of examples of those who thought a direct command could be violated based on what another command might mean and the message is crystal clear: Human speculation doesn't cut it.
For me, this was not hypothetical. (A child, a medical emergency involving blood and a believing JW wife.) I spoke with the JW parent organization directly and in the end, they acknowledged that the teaching is an interpretation.