Celebrating their reformation from the USSR was a primary reason for displaying Soviet symbols for many of them.
You confuse Europe with EU. For you, Poland was not in Europe before 2004. Pretty nice comment. Likewise, countries like Serbia, Montenegro, etc. don't belong to Europe. Go to Serbia and tell these people they are not in Europe.
Sure. Try displaying Ku-Klux-Klan's or al-Qaeda's symbols in the USA. You will see what will happen.
Germany belong to EU. Try displaying any Nazi symbols in Germany and you will see how well the police will be protecting you

I know China does not fall into your category but you can go to China and try displaying Kempeitai's symbols. Are you sure all parts of your body would be found after that? You are just a free man and you would expect the Chinese to be tolerant.