Every settlement in the Springer universe was a Hat Settlement. (Not a Hat Planet per se because some planets had more than one culture on them.) So even if you hadn't heard from Sparta Colony in 300 years, you were aware that Sparta was settled by people that had modified their culture via magic amazingly effective sociological manipulation to follow the ideals of the colony's founders. Thus when contact is established, no one is surprised that Sparta Colony is full of militaristic pederasts.

And one of the points of the series was that everyone was indeed seriously prejudiced about other cultures.

I don't really recommend the series. Like most of Barnes's work, it varies dramatically from book to book in quality. E.g., between the first book and the sequel he managed to forget most of the protagonist's defining character traits.