One can hardly disagree with Perry's argument -- except perhaps to state that the Serbs only sinned more than other Balkan ethnic groups chiefly because they had more weapons at their disposal. The Bosnians and the Croats are certainly no oil paintings when it comes to dealing with their local ethnic minorities. The Serbs were just more efficient in the ethnic cleansing department.
I'm not very optimistic as to the impact of domestic war crime trials on Serbian attitudes. It is quite likely they will be perceived as some kind of quid pro quo. For 99% of the population, whatever went wrong will always be the other guy's fault. Serbs are no more likely to believe that their lot ever committed war crimes than fanatic Zionists are to admit that Jewish terrorists are as evil as Palestinian ones.
People get awfully hot under the collar about these ethnic issues, unfortunately.
What makes the cetnics different was that they were organised from the top in a systematic way rather than just local hotheads doing bad things, the later of which was (generally) the case with the Croatian and BiH forces. In fact the fascist HOS militia, the closest Croatian outfit analagous to the Serbian paramilitaries, were almost completely wiped out in Vukovar or shortly after early in the war (and in fact they were not a tool of the central Croatian HDZ government but rather the HSP party). Although all sides did some bad things, it is simply not true that everyone was as bad as everyone else in the Balkan war.