As bad as things have been since Putin made the move to back Assad, they aren't nearly as bad as they would have been had Putin done nothing. If Putin had stood back and allowed the US to do whatever it wanted, IS would be controlling the whole of Syria and Iraq and with designs on plenty more. The head choppers would have spread and spread and spread. Putin and Assad were as surgeons removing a malignant tumor on the Middle East.
Let me also make it perfectly clear that IS would have wanted to take down the fake that calls itself "Israel." It would only have been a matter of time, not that I'm any fan of that fake Israel or any fan of war.
Humanity needs peacemaking, not warmaking. Anyone who says otherwise is damning himself or herself or itself or them or whatever the pronoun.