[mountainb]

It's because feudal is a technical term that has a long and misleading history of being used as a deliberately confusing term of abuse. The professors get ornery about it because they have to clear up the same misconceptions every year. For "dark age," many professors also try to take the opportunity to revise their students' perspective by deliberately highlighting brighter themes of art, philosophy, and so on to jazz up their introductions.

Part of that is just that particular specialty trying to make a case for itself in contrast to the more popular classical and modern periods. Then there is the complexity added by the fact that the classical era never really ended in toto; it just stopped being as evenly distributed.