Thanks for providing the quote:
... you will observe that the prohibitions in Acts 15:29 each relate to the way a person can defile himself in God's eyes. If a person takes into his body that which is unauthorised then he contravenes God's law, whether this be by eating food sacrificed to idols, by taking in blood, or by eating things strangled, or even by divinely prohibited sexual relations.
There are two problems here, both of which (IMO) are pretty severe.
1. Open conflicts between one Bible writer and another are not compatible with the JW view of the Bible and their understanding of its inspiration. Paul's more emancipated view at 1 Corinthians 8 must therefore be harmonized with the Decree and to that end, the JW parent organization offers the following explanation:
"What the decree in Acts:15,28,29 forbade was a Christian's being part of a formal, religious ceremony or his committing an act of idolatry." (The Watchtower October 15, 1978, p.30)
In other words, it did not matter if a pagan priest had uttered some mumbo-jumbo before slitting the animal's throat as long as the meat was not eaten as an act of veneration towards the idol.
That is all well and good, but the JW parent organization cannot have it both ways. They cannot on one hand, claim that the meat is defiling in and of itself while on the other, claim that the real issue is not the meat at all, but the finite act of idolatry done in connection with it.
2. Another facet of the same basic problem is the use of the term, taking in." Referring to disparate acts in generic terms implies an equivalency between them without actually having to demonstrate it, which is the fallacy of equivocation.
Drinking a glass of water and drowning in the ocean can both loosely be described as, "taking in water," but there is a world of difference between taking water into your lungs and taking water into your stomach. The two acts are not physically equivalent.
Similarly, there is a superficial similarity between sex with your spouse and sex with some other person to whom you're not married, but there is a world of difference between marital sex and adultery. The two acts are not morally equivalent.
The relevance to transfusion should be obvious here. There are demonstrable moral and physical differences between the transfusion of blood and the consumption of blood.