... I applied some google-foo and not having empathy is one of the defining characteristics of sociopaths, and then the first definition given seems pretty straight-forward:

The ability to understand and share the feelings of another.

I'm happy with that definition, and it doesn't change much. On the one hand, to understand the feelings of another you've got to have a good model for their preferences. Then sharing their feelings is the human/connection aspect of it.

In relation to this thread, I would refine that (perfect) empathy would be more than enough to be moral since understanding another person's preferences is the first part of it. (I don't think the second part is necessary for morality, but it makes it more natural.)