Eh, why not. By all appearances the ISIS militants are a collection of foreign fighters who could just as well end up facing our troops eventually, as they loudly promise to, so killing them to save the Yadzids sounds fine to me. I really don't think you are going to pacify the real hard core of ISIS with Ron Paul levels of intellectual engagement. Not when ISIS has started genocidal massacres.

Negotiating with them or eventually recognizing any legitimacy with them is like the Khmer Rouge, never a good idea. It might be beneficial to the US to do so at some point, but morally, no, gotta write those assholes off.

Yazids sound like they have their own issues though. Humanitarian aid and airstrikes, but no American blood on that situation.