Croatia isn't going to extradite anyone for defamation, even if there was a clear-cut case. Extradition is used when someone has committed a major crime in a country (murder, rape, kidnapping, spying, etc) and then leaves that country to avoid prosecution. And even then, it requires time and court appearances and agreements by the host country... and that is assuming that there is already an extradition treaty in place.
No country is going to arrest you and go through the trouble of setting up an extradition just because you put someone on blast and they're upset that people found out things about them. It's more likely that Croatia will offer to extradite Evans to any country that will have him, just to be rid of him.