Not only has God commanded that man should not kill, but He has also commanded that he "puts to death and brings to life". So to believe that active euthanasia is acceptable is to believe that it is all right to assume the sovereign rights of God. There are also no aspects of the U.S. Constitution that give citizens the right to kill. In fact, the right to life is stated as an unalienable right.
Many believers in euthanasia emphasize that it is a way to avoid the misery, but we must remember that pain and suffering is apart of life that we must endure. We are not to avoid evil, specifically pain and suffering, because suffering brings about perseverance, character, and hope. We should consider the suffering a time to strengthen our faith.
Although advocates of euthanasia say that euthanasia is good because it ends suffering, but it is important to keep in mind that the end does not justify the means. Humans are not animals, and therefore should not be harvested for the "best". It is believed that we should weed out those that are ailing, and in some peoples' mind undesired, people in society. To weed out the undesired people in our society is good in the eyes of some, but to nonchalantly kill the suffering is not.
To conclude, those that are advocates of euthanasia only think about the overall result of euthanasia: The death of another human being. Euthanasia frequently crosses the lines of moral codes and unalienable rights given to humans.