But your parents aren't English
Beh, it's the same language but we're too fucked up to admit it. Americans say they speak English because it is English.
Here we all speak the same language but we in Croatia call it Croatian language, Bosnians call it Bosnian, Serbs call it Serbian and Montenegrins call it Montenegrin
The reporter, before he asked him the question, said that Zlatan speaks the same language as him. And since the reporter was Serbian the guy who uploaded the video (and who was obviously Bosnian) wanted to make it clear that Zlatan speaks Bosnian, not Serbian like the reporter thinks.
And then people wonder why there are always wars in the Balkans