Go to war or don’t go to war: it amounts to the same thing. Intervene, and the deaths will be collateral. Don’t intervene, and the deaths might have been preventable. So long as ISIS and Assad are intent on having a war civilians are going to die.
Conventional warfare normally looks like this: you cost the enemy so much that they have to come to the table, and accept terms they would otherwise reject because the threat of further losses is too great to risk.
This strategy is not viable.
The Caliphate seeks to create a state under a radical, neo-traditionalist interpretation of Islamic scripture without the corrupting influence of ‘modern’ philosophy. It does not matter if this influence is from the West or Muslim scholars. This state will then provoke the ‘armies of Rome’ into a battle at Dabiq, which is supposed to precede the apocalypse.
Anybody who opposes, disobeys, or resents the law of the self-appointed Caliphate is a potential victim. Gays, Christians, women, Jews, free thinkers, and any Muslims who doesn’t accept the Caliph as their sovereign, can all legally be killed under their law. There is no room for negotiation.