::::It does not matter if it was there for years, especially when it violates WP:ASF and WP:NPOV in general. 
 ::::Russian historians are reliable sources too... 
 ::::There is no way you can go around WP:ASF if you insist on adding the word mass. 
 ::::Also, as has been mentioned before, what does the word mass mean exactly? Hundreds of rapes, thousands, hundreds of thousands? Keegan does not use the word mass. He mentions estimates that, as you have been saying, belong in the footnote. -