Do you think it is a vain hope that one day man will find joy in noble deeds of light and mercy, rather than in the coarse pleasures he indulges in today -- gluttony, fornication, ostentation, boasting, and envious vying with his neighbor? I am certain this is not a vain hope and that the day will come soon.
If we are defined by reason and morality, then reason and morality must define our choices, even when animals are concerned. When people say, for example, that they like their veal or hot dogs too much to ever give them up, and yeah it's sad about the farms but that's just the way it is, reason hears in that the voice of gluttony. We can say that what makes a human being human is precisely the ability to understand that the suffering of an animal is more important than the taste of a treat.