There were plenty of state controlled land east/south of Donetsk. You can check map here http://www.bbc.com/news/world-europe-27308526
Further, to even entertain this question, you have to believe that Ukraine positioned BUK launchers in the most heavily contested part of the country, in areas which were apparently held by rebels just weeks earlier.
This does not look like a serious controversy. The rebels shot the plane down.