As they say, those who cannot learn from history are doomed to repeat it. Once the EU drove Yugoslavia into a civil war with a divisive policy that sets up one ethnic group against the other.
In 1991 EU nations secretly supported separationist preparations in Croatia and Slovenia. Then they prematurely recognized them under the excuse that Yugoslavia had dissolved: a distortion of the situation and dangerous exploit in international law that could be used against any multi-ethnic country. But perhaps the most dangerous was that the EU adopted the self-delusion that everyone would follow them. In fact nothing changed on the ground in Yugoslavia except that one side had gotten an ally and the other an adversary.
Rich provinces all over the world try to secede in the knowledge that they will be even richer when they no longer have to subsidize the rest of the country. In the case of Croatia and Slovenia there was the additional appeal of a speedy EU membership. Given these circumstances the secession of Slovenia and Croatia was probably unavoidable unless the EU adopted an explicit policy that took attraction of a speedy EU membership away. Instead the EU fell for Croat and Slovene propaganda that tried to paint their secession in moral colors. Milosevic was painted as an extreme nationalist. He wasn't. He was just asking what most politicians representing an underrepresented large ethnic group that felt discriminated against would have asked. His political methods weren't always nice, but he was faced with political adversaries in other republics who had extended their power far beyond what had been intended in the Yugoslav constitution. His involvement in mass urder in Bosnia was still in the future: for the moment his policies in Kosovo were very similar to Croatia's policies towards its Serb minority.
A sound policy would have taken a distance and let both sides struggle it out in the political arena. It would have stressed that without an agreement the republics were still part of Yugoslavia, but it the same time it would have discouraged violence or rigorous steps by the central government. Instead the "moral" view of the EU led to immoral behavior. It now considered the rebellious Serbs in Croatia as insurrectionists instead of one side in a conflict. And it discarded Croat discrimination as primarily Croatia's "internal affairs". The result was predictable: Croatia didn't see anymore need for caution in its treatment of its Serb minority and the Serbs didn't see any other way than armed conflict to achieve their goals. Bosnia's war started in a similar way.
One would have supposed that more than a decade later the West would do better with Kosovo. Instead we see exactly the same pattern. The EU again couldn't resist the temptation to choose sides: this time by recognizing Kosovo. It could have chosen a neutral position and appointed a neutral mediator, but instead it appointed Ahtisaari whose misguided principles ("Kosovo should never again under Serbian rule") made any other outcome than unilateral independence impossible. A real neutral negotiator would asked the Albanians to convince Serbia that the rights of the Serb and other minorities were guaranteed.
Now too the real bad things happen afterwards when the EU has no longer the capability to see the behavior of both sides in the same light. Where in Croatia the EU crossed the line with its ignoring of the maltreatment of Croatia's Serbs, it seems now poised to cross the line with the privatization of Brezovica. Anyone can see that that will inevitably result in the end of the employment of many Serbs there. Past actions, like the evacuation of the court house, concerned symbols. Here it concerns directly the survival of Kosovo's Serb minority. And just as in the past the EU hid behind declarations about Croat "sovereignty" it now hides behind Kosovo sovereignty and the Ahtisaari Plan.