Is the term "Slavic" insulting?

Asked by travelbabe24 (262) February 10th, 2016 from iPhone

I’m just wondering. Today I met someone who is from Croatia and they were teaching me some Croatian words. I then said “wow! Slavic languages are so difficult!” The person then got real quiet, almost as if I have insulted them. But I didn’t mean to if I did!

So should one avoid to use the term Slavic? Is it a slur? Or insulting?

Thanks!