We should intervene to stop ISIS atrocities in Iraq
I don't agree with the language of intervention. It enables one of the narrative-determining untruths of Assad's war on Syria, that empowering the FSA with the weapons to stop Assad's attacks would be a rerun of the Iraq invasion. Indeed that is the point, the willingness to allow Assad to drag Syria further over the brink is what has caused region-wide instability and sectarianism, which in turn rehabilitates the idea that the West should sort things out. 
"The crisis in Iraq is a direct consequence of the disaster which has engulfed Syria for the last three years. In the aftermath of war crimes committed by the Assad regime, including the widespread use of chemical weapons and ‘barrel bombs’, the West at large – unlike me – remained unmoved by the suffering of the Syrian people, despite the fact that their plight was transmitted to millions of TV screens daily and dominated internet news around the clock.
Regardless of that, intervention was spurned by the British and American people, with consistent polls demonstrating a public consensus against the use of military force to alleviate the effects of the awful civil war.
After that, support for more extreme groups, such as ISIS, grew. Pro-Western rebels, such as the fairly moderate FSA, were usurped by assorted Islamists and radicals. Suffering tends to push political opinion towards the fringes, and the Syrian people have suffered more than anyone would wish upon them."