As a witness I would have just said the point remains the sacred nature of life, the blood being respected was just a symbol of that sacredness. It really wasn't about the blood, it was about the life. Blood was being used as a symbol of life.
Watchtower doctrine treats blood as a sacred substance because of its use in Genesis 9 as equivalent with life. A fatal flaw in that proposition is that the equivalence was said of the blood of living animals killed to eat and not of all blood. Specifically I have in mind the massive amounts of blood that would have been freely available all around Noah and his descendants in the form of animal carcasses dead of natural cause. That food was for the most part as edible as flesh of animals killed as food, and that food was loaded with blood, blood the text of Genesis 9 presented no prohibition against eating. This single piece of information obliterates an notion that the biblical God holds the substance of blood as some sacred stuff. He doesn't.
There's another thing often overlooked in the Genesis text about food where God grants permission to eat blood. It's the text of Genesis 6:21. Take a look at it. Think about all the stuff that is eaten as food by creatures and humans. (See: God gave Noah express permission to eat blood and Blood doctrine – thrown under the bus )