I don't think he is an idiot, he is true to his principles. If Corbyn had been leader no Afghanistan either.
Who wants to invade Syria?
Obama is under massive pressure to go to war. IS know this, so they are now baiting the West, as they would love a Western invasion. Thankfully, Obama is also sane, but there are plenty of voices urging invasion, and if IS mount another atrocity, he may have to give in.
Cameron is just being an idiot, when he says that killing Jihadi John struck a blow at the heart of IS. Wow, and this guy is making the decisions? Help.
Hopefully, in the background the intelligence people are actually thinking about the Sunni revivalism going on - how do you deal with it? If it isn't dealt with, IS will flourish. The Sunni arc stretches from Iraq through Syria, into Turkey, and of course, the Saudis. Where else do IS get money and supplies?