Since the 1930's there haven't been so many civilian aircraft shot down by military anti aircraft units, some 10 or so. However, those that were shot down, caused great lose of life.
So civilian aircraft don't by intent fly over known war zones, they either stray from their navigational path or become victims of chance or coincidence.
Some nut with an itchy rocket finger loses contact with sanity and fires a rocket at them or scrambles a jet fighter, piloted by the squadrons biggest head-case.
Yes, all caution is take to keep civilian-aircraft away from war zones and that was also the case with flight MH17. However, the crash investigation in this instance, has uncovered who the perpetrators are and they will in some-way be brought to justice. That they are Russian, is just coincidence.