How being called an Easter European can be an insult?
If I'd call you gay it would be an insult because you are not gay.
If you'd call me Eastern European it would be an insult because simply I am not one.
I couldn't explain it any simpler so I hope it will help you to understand.
The language,
oh wait so what is according to the UN Romania with romance language doing in Eastern Europe and where is Slavic speaking Serbia?
cuisine
well ofcourse, even Polish national dish is Germanic
culture
what culture? Religion? Poland - Catholic, Eastern Europe - orthodox