Euthanasia is illegal in a lot of western countries, and in those it is legal I don't think it is permitted to just kill a person in such a way. Ultimately its about choice. A few years back it was legalised in Australia for a brief time, and it wasn't about getting rid of old people, ti was about giving the terminally ill the option to end the pain and indignity of what they were experienced. So I don't think it could be used to just remove old people.