A leading Lutheran physician, Dr. Rudolf Boekh, explains that the destruction of "lebensunwerten Lebens" (life unworthy of life) is a decision best left to God and whomever God has appointed to the task.
Dr. Boekh says:
"These distortions of the human image" should be "returned to the Creator. ...The decision about whether a person should be destroyed belongs solely to the man who under God has been given the power to do so. ...That can only be the Führer."
Rudolf Boekh is the chief doctor at the Lutheran Neuendettelsau Asylum in Central Franconia, which means he's ultimately responsible for the welfare of many handicapped and disabled people being treated there.