It is manifestly clear that the idea that the EU equals security and Brexit equals isolation (splendid or otherwise) for Britain is complete bunkum. It should be perfectly possible for the major players to cooperate against ISIS as national governments, within or outwith the European Union, and to work together closely, without the need for an ever-expanding and self-serving EU superstructure.
But then the inability to see this is at root what is wrong with the EU more broadly, and the reason the UK is having its referendum at all. Even when Britain talked of leaving and tried to negotiate a distinct set of arrangements, and suggested that the federalist mantra of Jean-Claude Juncker and co is a dead end, it did not seem to produce much of a recognition of reality. Speaking as a European (who is nonetheless sceptical of the EU, which is not the same thing as Europe) my concern is that what has been constructed is transparently unfit for purpose. It is a botched bureaucracy, built on a notionally nice idea, being rendered inoperable by history. The EU open borders model and obsession with anti-democratic integration rather than trade and friendly cooperation is turning steadily into a catastrophe for European civilisation