Both Croatian and Serbian societies are infected with radical and nationalist ideologies, most commonly fascism and neo-nazism. However, nobody will call the ideologies by those names in Serbia and Croatia, they just call themselves “patriots”, “conservatives” and “monarchists”.
In ex-Yugoslavia, ultra-nationalists were imprisoned, which was one of the contributors to the ethnical stability. Basically, they were kept away from the political power.
The ultra-nationalists are the ones who divide our societies. People need to realize there is no way to define your ethnicity by blood, especially in the diverse areas such as Balkan.