Unfortunately, NATO forces were needed to stabilize tense ethnic cleansing initiatives take on by members of different sides of the conflict. NATO's bombings were unfortunate and they did exacerbate tensions in the war. However, the region is more stable now that many countries exist and ethnic people can live where they want to and they can exist peacefully.
Throughout history wars have often been caused by an attack by outside or opposing group. The other side has to defend itself by attacking back. It is natural for a group or individual to defend itself. For this reason I believe the bombings exacerbated the war and made it worse.
The NATO bombing definitely helped to stop further genocide during the conflict, which was already taking place and was already atrocious. How could the NATO bombings have made things worse in Kosovo - there was already a genocide taking place, what could really have been worse than that in the end?
I do not believe the Kosovo War was exacerbated by controversial NATO bombings during the conflict, but they certainly didn't help the situation. These bombings are controversial because they killed a decent amount of civilians, which is unfortunate. The bombings were never supported by the UN either and never formally approved.
No, the Kosovo War was not exacerbated by controversial NATO bombings during the conflict, because NATO does not act unless they have carefully measured their response. The actions by NATO were helpful to end the conflict, not to have it continue. The bombings were calculated to bring about an earlier end to the war.