Seriously, what do US policymakers have against supporting the Kurds? Are they just not aware that that's an option? I mean, I understand that the Kurds are pretty politically radical, especially in Syria, but that shouldn't prelude US support of their campaign against Da'esh. And what a campaign that has been. The peshmerga are the only military force in Iraq or Syria that have managed to consistently push back against Da'esh's advances. They won historic victories in Kobane and Sinjar, and there's something deeply satisfying about watching the empowered women of the YPJ defeating those who would see them covered and kept in the home. So why won't the US aid the Kurds?
Because they don't want to piss off the Iranians and Turks? It's not far from greater Kurdish power/autonomy to a Kurdish nation to a Pan-Kurdish nation. I'm unsure that adding another side to support in Iraq is popular in general, either.
I think you delved a little bit into it there. If the US has been consistent about one thing throughout the years, it has been its lack of support for - and even opposition toward - leftist revolutionary movements. Another factor, especially in Iraq, could be the politics of supporting the independence-minded Kurds while also pleasing the Iraqi government and the political elites that dominate it. I'm pretty ignorant about the Kurds, but from what I've read, I like them more than other rebel groups in Syria and Iraq. Edit: Also, like Quatrarius said, politics with Turkey and Iran.
The whole situation over there is pretty effed with ISIS... so long as we go into this with diplomacy in mind I would support aiding our allies in defending this threat. I do get concerned about how many recruits ISIS is managing to muster despite our bombing runs and I wonder if boots on the ground would cause more harm than good (it can be argued that this has been the case thus far in the middle east). Either way, I know we can't just keep banging our heads against the wall with air support if it is not effectively reducing their sphere of influence.
I was in the exact location in which they are building bases in 2007 and 2009. What an unfettered hell hole that place is. No wonder it bred extremism after we knocked off their dictator.