It's interesting, but its claim may be flawed. The fact is, to the absolute best of our ability to judge, neither gods nor dead people actually exist. So it is not the case that there exist entities that have been pushed out of the circle. On the other hand women and minorities and cats do exist. And they have to various extents been brought into the moral circle. To the extent that the categories of existent entities and morally relevant entities have increased their overlap, that's progress. Or it's at least movement in a consistent direction.