The fact that the symbols used by the Ushtase were in use for hundreds of years prior to their use by the Ushtase doesn’t change the fact that they became so tightly associated with the ushtase that they gained a Nazi connection. The swastica was also an ancient symbol and yet it cannot be displayed in Germany or the western world today without having a Nazi connotation. So, when the Croatian’s started to display these hated symbols again it is no surprise that Serbian civilians reacted just like Jewish civilians in Germany would react if the Germans took to flying the swastica again.
The Swastika wasn’t used by the Germans prior to the rise of the Nazis. The Croatian checkerboard had been used for hundreds of years prior to the Ustashe. The Serbian accusation of Nazi connotations with the Croatian flag is pure BS.