Humanitarian Crisis or Cossack's Revenge?

So how is it that as soon as  the politically incorrect side approaches success in a military confrontation, be it in Gaza or Ukraine, the losing side and their external supporters start squealing about a humanitarian crisis?

The latest headline is that Ukrainian military forces have effectively surrounded Donetsk, the "capital" of the so-called Donetsk Peoples Republic and are responding to requests for a ceasefire by essentially telling the rebels "Sure, surrender and we'll stop shelling."

After 200 some years of brutal cultural supression and having been driven from their homelands by mass starvation and mass deportations only to see ethnic Russians moved into their homes to fill the void apparently the Cossacks are in no mood to have the very lands themselves stolen as well.

The Russians and the world in general has forgotten that the Cossacks (Ukrainians) have a long history as some of the most fierce and fearsome warriors.  Or maybe Putin and company do remember and don't want to commit to a full scale military confrontation for fear of getting a very bloody nose and perhaps having troops say "no thanks" to deeper involvement as happened with the Russian's debacle in Afghanistan that ultimately brought down the Soviet Union.

Could it be that there remains a disiplinary weakness in the Russian military that Putin does not want exposed to the rest of the world?  Historically the most feared "Russian" units going back to the time of the Czars were actually Ukrainian Cossacks.  A claim that they may no longer be able to make.