I was appalled with the dialogues from the "nobles" and the old priest, so much hatred and ignorance. I´m aware that gypsies are not saints, but it was really very insulting words, also including anti-semitic insults. By the way, in the movie they say that gypsies are from Egypt, but thanks to genetics studies, we know today that they are from Northern India.
shareIt is the characters in the film who are ignorant, not the filmmakers and writers, as I'm sure you're aware.
shareIt is known even before the genetic studies that gypsies come from India, and as tbrainerd said, this is only to underline the ignorance of the characters.
Also, please take in consideration when the action is taking place. I could give you much more examples from XX century USA and Europe.
Yes, it was known before widespread DNA testing, by comparing the Roma language to languages in regions of northern India.