It will take brutality and collateral to deal with ISIS – Russia has a higher tolerance for that than the west. The west doesn’t want to get its hands dirty, or at least not directly, so they just arm people and then look the other way.
As for Russia not attacking ISIS, they’re attacking all opposition forces to try and restore order. I doubt they’re even differentiating between them, and just hitting the best targets as they present themselves.
Arm people and look the other way? You decide to completely ignore any statistics on missions flown, ordnance dropped or ISIL tgts destroyed then?