Hello! Glad you asked me.
The reason why your neighbors are still upset is because the biggest "insult" or thing to ask a Bulgarian, is to mention the Russian alphabet and speak Russian instead of Bulgarian. Bulgarian and Russian are two totally different languages. People usually mess them up as one because they are both Slavic languages and sound similar. Bulgarian's think it is an insult when you say, "Are you speaking Russian?". I really dont know why but xD
Hope that helps
I found a better explained video if you want me to share it.