It's tough for people to see a live animal being fed to anything besides a snake. And even then, people get offended. I don't like killing any mammal. Even though I'm starting to feed my guy frozen, I guess I somewhat take comfort knowing someone else did the dirty work.
People like to make the assumption that mice will tear up and/or injury these animals, but truth is, they do eat these in the wild and I'm sure a few scratches will heal quickly or do little damage to them. I have fed live feeders to fish that has been sick, but I see them as predators and predators feed on the weak and sick in the wild. I haven't lost a fish ever, due to a "bad" feeder. I'll probably be crucified for admitting that, but again...people have different views and you can't change someone's opinion unless they are willing to accept it. And when it comes to live feeders...there may be a lot of different reasons for doing it and unless they are willing to accept the reason, it will never settle with them.