I'm perfectly Russian and I'd still not like being called that all the time. Especially from a foreigner. If you offended him... It might be too strong of a word, you might have made the conversation unpleasant but offensive... Depends on a person I think. Your intonation could have had a big impact as well. If he somehow noticed any scent of superiority in your voice, that might have made him very mad at you.
As maxmixiv noted there's hardly any reason to not call someone by their name.