I feel like the people with the strongest stance against feeding live are probably also either vegetarian, or at least concerned with the welfare of the animals they eat and search out more ethical sources. Or I'd hope so at least. So your point of "you think this is bad? well here are some other things that are bad!" is not a very effective one.
It does, however, highlight the point I brought up earlier, which is that the way the animals are kept and treated while they are alive is a thousand times more relevant than how they are dispatched, since that part is very quick either way. I have seen some rodent breeding operations where half a dozen or more adult rats are kept together in a poorly ventilated ten gallon tank or tub and fed nothing but those corn by-product "rat pellets." That should be far more concerning than people feeding live. From browsing that area of the forum, I get the impression that most rodent breeders on here have more ethical set-ups, but I have to wonder if that's the majority.