I don't see any reason to get banned for this,really.But didn't they told you to put it off and never got reported with it again before they ban you?I mean it's stupid to ban you for this,and not even telling you.

Btw,it's just a flag,a simbol,nothing more.We are free man,and we have to look straight to the future and don't do the mistakes of the past wich people faught for flags and relegions.