this is somewhat a moral situation. For many people taking one life to save many is unreasonable. Imagine if YOU had a genetic oddity which was causing you to produce antibodies to some horrible virus, for the sake of horrible lets say HIV. Now that's all good and fine but inorder for it to be useful they have to extract it all from you which would leave you dead. Do you think that situation is alright where the government just says "kill him" for the lives of people you probably don't care about? The reason i'm anti-abortion and such is that these people haven't had the opertunity to live at all. These people suffering from alzhiemer's amung along with several other diseases have already lived far fuller lives, and in some cases are already beginning to see the end of their lives naturally anyway without the disease in question.