jim360 - //A refusal to engage in military action is as good as acknowledging their legitimacy as a nation.//
That assertion holds no logic at all.
If IS wish to believe that they are acknowledged as a nation, then let them believe it - that costs nothing.
If, as your argument suggests, that military action infers that we are not impressed with the IS plan, then that is a seriously expensive, in terms of money and lives, way of making a point.
The facts are very very simple - military intervention, has not worked in the past, and will not work in the future.
I do not know what the solution is, but only someone with a vested interest in military action - such as the generals whispering in Whitehall ears - would seriously argue that military action is the way forward - based on extremely recent experience.