Actually for a lot of people who chose not to eat meat the pain inflicted on animals is a significant part of the problem. I don't think there are too many people who are arguing that an animal life is the direct equivalent to a human life. I would actually argue that for animals, torture is worse than death but for adult humans the reverse is true. This is because the value of a human life is significantly greater but relative ability to feel pain is likely to be a lot more similar. It isn't really fun to logically delve too far into this which is why I guess a lot of people don't do it.