Well... if you consider it to be "do to others as you would have them do to you"... then euthanizing another is what you would have had them do if you were in their situation. I don't know about endorsing it exactly... but it kinda makes sense to those who are party to the "golden rule", which is that "money rules the world" or that "gold always goes up" 
Please give me a home where cloud buffalo roam
Where the dear and the strangers can play
Where sometimes is heard a discouraging word
But the skies are not stormy all day
