East had no prior experience with migrants due to living for decades in effectively prison camp guarded by soviets, no travel or other exposition to other ways of life. We were very monolithic cultures (and still mostly are).
The voices were completely ignored and overruled by behemoths like Britain, France and most powerful voice in the bloc - Germany.
Don't revision past, I lived through it, saw masses of people getting absolutely mad pissed off and feeling helpless and unheard with arguments which over time proved them mostly correct.
I don't hold those opinions myself, some of our best friends are muslim immigrants but oh boy go to the eastern EU without camera and ask random folks on the street outside capitals, or just listen to them. Or look at election results, this gave russians and their constant influence very good arguments since they position themselves as 'guardians of traditional family values in society', regardless of how its true or not (clue - its not but thats detail here).