They're not targeting civilians; they're targeting IS bases, or I should say, they have already done so with complete success.
OT: Unfortunately, this is the only way. With IS, there can be no resolution through words because they're greedy and sociopathic in their ways.
With that in mind, their only options are to try and reason with them fruitlessly, and constantly for a long period of time, whilst they go on killing, or to end their reign of terror as quickly as possible. You have to understand that IS aren't like Russia or China; the aforementioned have self-preservation, a comparatively calm demeanour and a certain level of reasoning - IS have none of these traits.
You may as well talk to a brick wall covered in TNT; because they don't care about any lives; not even their own. It's just one of those situations in which the end justifies the means. The human concept of morality is yet to be complete at an intricate level, hence why it seems illogical.