Remember that morality in battle is defined by the side willing to go the lowest. Fighting back by killing innocents is sufficiently low that I will not question anything Putin chooses to do at this point. Terrorists can call themselves what they will, they must be completely destroyed. (Bush are you getting this?)
The Russians have already set the bar low. The Russians have killed thousands of Chechen civlilians.
What are a people who do not have the firepower to strike back supposed to do?
Machiavelli once said "Do not do your enemy a small injury". I.e., do not injure your enemy enough that you've pissed him off, but not enough to affect the enemy's ability to retaliate.
Rome understood this in their dealings with Carthage, where they finally took Carthage, killed the men, enslaved the surviving women and children and dispersed them throughout the Empire, and finally leveled Carthage and spread salt on the site so nothing would ever grow there again. They had no further trouble with Carthage
The Muslims will be pissed off and in the mood to kill Russians as long as there are any left alive