Dturn - I remember when I was about 18, I took my cat to the vet after being hit by a car. He was paralysed in the back legs and up the spine. My sibling (15) had come with me for moral support.
The vet gave me the facts and recommended euthanasia. My sibling started screaming at him for "not even trying". There was no chance of recovery for the cat and we had many at home as my mom did rescue work. He knew the answer my mom would want and had given me that same answer. How was he supposed to know my sibling was a psychotic freak...
Fortunately, he did not hold my sibling's behavior against my mom or me. He was the best vet I've ever dealt with.
Oh, and when any of my pets need a blood infusion, I always bring treats for the donor cat. While, as my vet's office has said." they are here for just that purpose", I always point out that the animal doesn't volunteer, they get conscripted. They deserve the extra attention for helping my pets in their hour of need.