Because they revolted due to the intent of the illegal coup government. If they had not revolted, it would have been illegal to use Russian in official government documents. So it might as well have been. You cannot claim that a rebellion against an illegal government, has to make a legal declaration with the government of their intent to revolt. So no illegal war here. Just a rebellion against an illegal coup government that was trying to force 5 million of its people to use a different language. Fairly straight forward. No need for chaff.
So, then why did they kill approximately 300 innocent people, including children and infants? And, why are we hearing that the bodies and personal effects were looted and disrespected?
These people have been treated as exactly that - chaff.