According to reports, just shy of 400 Yazidi men captured by IS have been murdered in Kocho in Northern Iraq.
In my opinion, if we can bring about the downfall of these IS savages at the cost of arming, training and providing close air support to the Peshmerga without having to commit our own troops (save for a small special forces presence perhaps), then we should be all over it. Given the ideology IS follows, I fear that we're going to have to fight them sooner or later, better to do it now, before they can become more established.