From what Ive heard of snake husbandry, live feed isnt necessary in most cases, so the act is unnecessarily cruel. Before someone says that snakes kill in the wild, so do all other carnivorous animals, and most of those kept as pets arent being fed live food.
However, from a practicality standpoint, I dont have an issue with using (unfortunately) unwanted animals as food. Shelters get crowded, and if the animals were healthy enough but not finding homes, humane deaths used to aid in other animals survival is something Id find acceptable.