Kiev is using these mercenaries because their Army was and continues to defect.....those mercenaries were killing young men who refused to fight..... The Kiev opposition has mercenaries because their numbers were not sufficient to ward off the military might Kiev's been using against it's citizens.
I am fair - The pro-Russian side themselves has complained that they are getting no recruits in the Donets.
And they also admit they are using Chechens and others, who are most certainly not locals.
This is not popular on either side, that seems both correct and fair.