I just read a comment on the video on LiveVideo.com about this video and these croats are just unbelivable. One croat (and a proud of the crime apparently) try to claim that they didn't kill million serbs, but rather only 150,000 serbs and jews eventhough even Holocaust Memorial accepted that number. Well, that's easily solved and here's how:
You get the number of serbs before and after WWII and see what the difference in the population number. 1 million serbs cannot just simply disappear...THE END.
See, that denial by these croatian sick mf can easily be resolved. Of course, knowing that then they can't prove their point, I guarantee you that they will try to get out of it by starting a different subject, but if they start that before you, simply say "first answer this question and then we move on to another".
As sarcastic as this might sound, it is also the best way to catch them in a lie.