The truth is that there are times when I feel that criminals and children in third world countries should be put out of their misery. As someone who sees this life as a prison and death as a potential release into a greater existence, it's hard for me not to. On the other hand, I wouldn't want to force anyone to pull the proverbial trigger and my conscience wouldn't allow me to pull it myself.
I suppose darth_ender was right after all; it is easier -- or in his words, more convienent -- to take the life of an unformed being that has never developed a mind than it is to take the life of someone with a defined personality/human face.