In my quick perusal of the posts in this thread I didn't see this point made, my appologies if I missed it and am repeating.
As far as the question about if empathy towards the elderly or malformed newborns have some advantage or not, it's important to remember that evolution does not guarantee always choosing the "best" adaptation. For example, it's possible that having a general empathy includes the elderly is slightly less fit than having one that doesn't, but at the same time either type is more fit than having no empathy. Evolution does not guarantee we end up with the "most fit" empathy.
Plus, it could be that in one environment the first type of empathy is more fit, and in another environment the second is.