Batshit - comparing ISIS to the IRA is way off beam. The IRA weren't rampaging round Ireland, north and south, capturing cities, and imposing their own brand of Catholicism and legal system with mediaeval brutality. By focusing on the fact that they both initiate(d) terrorist attacks, you are missing the bigger picture. The IRA was ONLY a terrorist organisation, whereas ISIS is a terrorist organisation that now has a visible army, fighting in Iraq and Syria.
'Rout on the ground'. ISIS do not have an airforce. That is their opponents' main advantage. Why not use it? Strategic air strikes, as in Iraq, in support of the Kurds, is probably our best bet. Before GB and the USA started air strikes, the Kurds were being driven back.
My objection to 'It's all about oil' is it's the Stop the War's default position which they use, in a 'simplistic' and 'naive' way, to divert discussion of any potential Western intervention into an attack on the U.S.A. As you have done. Some of it, a lot of it, is about oil. Obviously, oil is important and to have people like Saddam or ISIS in control of it threatens everyone's security. But do you really think we should just stand by and watch unspeakable acts of genocide?