@roger,
That is not surprising. Bigotry is a fairly common trait that you see in human as well as many other species. I think that bigotry is common among social primates in general. When it comes to ensuring a constant supply of resources, there is a clear evolutionary advantage to bigotry.
There are many animals, including non-mammals, that regularly kill other species.
Cheetahs killing gazelles for sport (which sometimes they do) might be an example of bigotry. Ants killing beetles somehow doesn't seem like the same thing.
Ants in different colonies, even from the exact same species, will have brutal wars over resources.