They can always see some short movies about serbia at youtube.
I'm afaraid they will always pull these things as long as Nole is threat for their favors, especially after they found out how painful are this subject for us. You can see, they even don't understand why all these people from serbia favorize Nole only (and that's not the true, there are some of them who cheer for Nole's oponents), and that's nationalism for them. There are few guys who got it, it's because we are small country, and I should add: full of problems, especially in economy, coming out from several wars, need to improve itself.
I think it is impossible to discuss history in such a large context. When multiple people are laying down allegations, it is difficult to make an argument. If one honest person is interested in hearing a different perspective, then they will calmly discuss the issues post by post and you can direct them to alternative sources.
But when it's a feeding frenzy with sawan, allure, glenn and who knows else snapping at "those Serbs" and "Serbian fans the worst" - there's little that can be argued.