"You shall not eat anything that dies of itself; you may give it to aliens residing in your towns for them to eat, or you may sell it to a foreigner. For you are a people holy to the Lord your God. "(Deut 14:21)
I've also heard this one used a lot to excuse JWs benefiting from blood components processed as a result of 'worldly' people's misuse of blood. The application of this scripture falls down on several levels.
"You shall not eat anything that dies of itself; ... "
Nothing has died. The donors are living.
Nothing is being eaten and digested. The blood is being transfused and used in the body in the way God designed it.
" ... you may give it to aliens residing in your towns for them to eat, or you may sell it to a foreigner. ... "
The 'worldly' people can use the blood. That means JWs mustn't use the blood.
The law said nothing about aliens and foreigners carving up the unbled meat and giving pieces back to the Israelites to consume and that would be OK. So why are JWs using the blood given away for only 'worldly' people to use?
Besides, JWs do not give blood at all, so how can this be analogous to an Israelite giving/selling an unbled carcass to 'worldly' people?
" ... For you are a people holy to the Lord your God."
Holiness without hypocrisy. It is hypocritical for JWs to personally benefit from the result of 'worldly' persons making an industry out of breaking God's laws and principles on blood.