If the actions of the governments of the US, UK and other NATO member states allows Isis or al Qaeda to flourish, grow and gain a foothold in countries which they didn't exist in beforehand then I'd say that's a classic example of "causation."
I think he meant the bit about Cameron and Obama etc. Not the training with an ISIS franchise.
It's really quite simply, before the U.S. And NATO bombed Libya and helped the "rebels" overthrow Gaddafi there was no Isis controlled areas in Libya but now there is and this guy was trained there and killed dozens upon dozens of innocent people. How are they not partially to blame?