When ISIS had still been in a column in the desert, after just a day of getting to Mosul, that was when to act. He could've switched sides and sided with Assad and destroyed the ISIS cancer US policy created.
I suspect the anti-war crowd would've supported offing the genocidal maniacs created by US foreign policy of regime change because at that point it would've been an admission that the war mongering was a mistake.
Now, the only sane way out would be to work to stabilize govs we've destabilized, like the Egyptian military did on their own. Obama isn't going to that, because he's as much of a globalist tool as GWB was.
Actually, he should have acted when they took Fallujah in January.