The Greeks then and now look at the Macedonians the way New York and California liberals look at the people of Indiana, Kentucky or Tennessee. Of course it galls them to think their civilization was conquered, and then spread, by someone they would consider a bumpkin by heritage.
And I claim some expertise in this perspective as a half-Macedonian Hoosier.
A related issue, when I was stationed in Crete the Greek phone cards we used to buy had a little slogan on them I will never forget :
Macedonia is one and only and it is Greek.