Here some more food for thoughts of all those considering 'Assad the lesser evil' in Syria (in comparison to the ISIS):

Assad Policies Aided Rise of Islamic State Militant Group
The Islamic State... gained momentum early on from a calculated decision by Syrian President Bashar al-Assad to go easy on it, according to people close to the regime.

Earlier in the three-year-old Syrian uprising, Mr. Assad decided to mostly avoid fighting the Islamic State to enable it to cannibalize the more secular rebel group...
...which is precisely what I'm 'implying' since longer.

Perhaps some there in the DC might think twice before coming to the idea to 'cooperate' with Assadists now.