As far as I know the people of Kosovo were happy to be separated from Serbia...
So were the people of Crimea.
... They say that the Serbs made many ugly things in the Bosnian war and had to be bombed to reason.
The Sebrenica massacre and the "ethnic cleansing" among other things...
What happened during a civil war in Bosnia (Srebrenica, etc.) was done by ethnic Serbs who lived there for centuries, not the neighboring Serbia as a state. It would be like blaming Germany for something ethnic Germans who live in Austria did. Or Austria for what ethnic Germans do in Italy. In any case, Bosnia is not Kosovo, which was part of Serbia for millennia.
Besides, it is not the bombing we are discussing here, but the secession, which happened
nine years after the end of bombing. Note that about a half of the world states have
not recognized the secession, some European countries as well.
Here is a comment from the American Society of International Law (emphasis mine):
... while Kosovo's declaration of independence and its recognition by various states can be justified under existing international law, it is not a clear case. Rather, Kosovo presents a quintessential "tough case," demonstrating the ways in which political interests of states affect how the international law is given effect. How and whether it will be considered a unique case in international law or a precedent for other secessionist movements may depend on how various states interpret the law and facts that gave rise to the declaration.
Note the part about "a precedent for other secessionist movements," which is where my comparison to Crimea comes from.