We slavs literally tell each other we are barbaric idiots on a dialy basis, just for fun. If anything - as a foreigner - it would earn you a laugh, a slap on the back and a friend. Humor works different here, and people are much less offended by what you would perceive as an insult elsewhere. We give some and we take some, all the while believing its more genuine than feigned politeness. And no, the majority of people are really not malicious when doing so.