Logic by itself has no ability whatsoever to tell the difference between moral and immoral. It is not true that animals cannot tell any difference in this at all – only that they have limitations in this regard. It is true that we can rationalize things and animals cannot. It is the claim that our rationalizations add what you claim which is questionable. We pick our premises to get whatever rationalizations we want for whatever conclusion we prefer. The idea that only our rationalizations give us any moral responsibility is even more dubious. It is instincts and social relationships which give us moral responsibility and animals have both of these – to a far lesser degree I would certainly agree, but that is all. This is what our language and rationalizations give us – a measure of social interaction and relationship which far surpasses any of the animals. It makes our social environment far far more important than the natural environment. And if we compare it with the advent of multi-cellular organisms the significance of this cannot be overstated. It is life and evolution on whole different level.
Besides compatibility with scientific findings, there are the philosophical consequences of this to explore. In addition to cutting ties with the rational poverty of authoritarian morality, the above realizations give morality both a cultural, religious, and species independent foundation which greatly strengthens our grasp on morality itself – so we can distinguish the arbitrary relative elements of mere convention from those things which are absolute and essential. We can understand what kind of morality makes society function with greater well being for its members – for that is what we ultimately expect from a morality which we can all embrace whole-heartedly.