With empathy, it turns out that Germans were much more likely to empathize with other Germans than with Juden. With empathy, everyone was cheering as the witches burned.

Moral progress is the progress of knowledge. Slavers in the antebellum South convinced themselves that they were doing a favor to the slaves because the latter couldn't survive by themselves in an advanced economy. A hundred years later, they changed their minds more than they changed their hearts. We (some of us) have learned that coercion is almost always bad, making world saving plans that involve a lot of coercion tend to fail, and preserving people's freedom (blacks, witches and Jews included) increases everyone's welfare.

Is empathy part of one's motivation to even pursue moral progress? Perhaps, but if so it's a very deep part of us that will never be discarded. All I'm saying is that whenever you have finally decided that you should make the world a better place, at that point emotional empathy is a bias that you should discard when choosing a course of action.