Within a week of capturing Ramadi ISIS stormed the ancient city of Palmyra, destroying ancient monuments and killing anyone in their way. Despite, or perhaps because of the best efforts of the US and it's allies to defeat the ISIS threat they appear to be getting stronger, not weaker.
Or perhaps strength is not the correct term. ISIS are not problem which can't be bombed out of existence in the way a despot's military equipment can be, because their military strength is a manifestation of an idea which is largely accepted by a significant section of the population of the areas in which they operate. Short of killing everyone you can't bomb this support away and there's a strong chance that bombing will actually strengthen it. Iraq has been either occupied or at war, and in both cases heavily bombed, for quarter of a century, and it clearly hasn't worked.
When Lord Elgin was the High Commissioner to China in 1860 he quite effectively ended the second Opium War in part by ordering the complete destruction of the Old Summer Palace which was a potent symbol of Chinese imperial power. Either an act of supremely vindictive hooliganism, or a stroke of bubble popping genius. Possibly both. Either way the symbolism of it was, and remains, very powerful and arguably achieved what years of military campaigning had failed to do.
It's interesting that ISIS themselves appear to know this, and make a point of smashing historic monuments wherever they go, in much the same way as the Taliban destroyed the giant Buddha statues carved into the rocks at Bamiyan in 2001.
I don't know the area well enough to know what if anything could be done to similarly undermine the persuasive message ISIS put across, or even if this is the best approach; but unless you somehow remove the hold ISIS have over a large section of the population in the areas in which they operate we have no chance at all of destroying them.