Suffering people should be able to die. Elders with hopeless medical cases do not have to be subjected to painful living. Brain dead people of all ages are not a positive presence in humanity. People literally living off of machines should be allowed to choose their fate with a signature. They aren't able to correctly process what is happening? Their must be tests and circumstances, but people not willing to live should not carry the affliction of life. Life support spending in the U.S. is insane, only to keep hollow shells of formerly healthy and loved people alive. The people do not experience life anymore. Their families are only creating bad memories to accompany the good from a loved one's lifetime. Shells of people do not need to live.
Many people such as yourself use the argument of suffering people WANTING to die. These people may be influenced by treatment or suffering when they request for assisted suicide. It may not be a frank demand, and may be one which they will regret later and be pleased they were not granted, later on in life if they are may be cured. You cannot be certain that these people are in their right minds when asking for assisted suicide.
In the case of the brain dead, humans of all kinds of cultures, races and religions, such as Christianity, have accepted are developing world as it is today. Medical advancements have meant that we can keep people alive for longer, and perhaps long enough for treatment, or even a cure to be found. Moreover, medically speaking, doctors are obliged to do everything possible which will ensure the health and well-being of a patient. This is in agreement with the law and teachings for doctors in the UK (where I live). It is for the greater good of one's health- with technological and medical advancements increasing over the world, it is becoming more and more likely for cures to be found for the terminally ill.