Obama policy in Libya vs. Iraq

If I remember correctly, Obama ordered widespread airstrikes in Libya to stop the possibility of genocide taking place in cities like Benghazi if Gaddafi's forces were to retake them. Yet, in Iraq, with clear actual evidence of genocides taking place, we are only airlifting water and food to the Yazidis stranded on a mountain and only using airstrikes solely to protect a few dozen American personnel.

It seems like an extension of Obama's Libya "doctrine" would clearly support widespread airstrikes against ISIS, yet his political reluctance to reengage in Iraq is allowing the slaughter of thousands of religious minorities in Iraq. I know it's a messed up situation as ISIS probably wouldn't be in control of parts of Iraq if we never invaded, but we can't go back and change the past. ISIS clearly needs to be taken out as they are a serious threat to global civilization. Also, what message does it send to stand idly by and watch thousands of Iraqis get murdered but to use military force to protect several dozen Americans?