In Shakespeare’s Hamlet even a common soldier, Marcellus, can sense that “Something is rotten in the state of Denmark”. Similarly from the behaviour of the EU towards the first country to decide it wants to leave it should be obvious to all that something is rotten with the Union.
It could have responded to the UK’s decision just by stating that the benefits of membership are only available to those who pay their dues and follow the rules, so leaving would put the UK in the position of a third country. But then continuing that, as a past contributor and a close partner in trade, security and research, the EU would welcome a trade agreement with the UK as the best outcome for both parties and that since the UK is exactly aligned with its rules to start with this should be at least as good as those with Canada or Japan, if not better.
The reaction of a self-confident Union to Brexit would be: “Good luck with that, sorry you’ll be missing out on our great future”, but amongst the EU’s ideologues there is an apparent desire to punish the UK for its apostasy, or at least a wish to prove to others how bad the consequences can be for anyone who threatens to leave. The EU’s obduracy and threats demonstrate a profound weakness and lack of confidence in the success and benefits of the Project. If it were as good as they pretend who would want to leave?
That some things are wrong is not necessarily denied by Remainers. However, they believe in the potential of the Union and the possibility of reform so that the plan will come to fruition and the benefits will arrive in time. We don’t share their confidence that the EU can be reformed (see Can EU be Reformed?). There has now been sufficient history and it does not support this expectation. The benefits have been few and minor, certainly for Britain, and for some other countries membership now looks dangerous.
The weakness has been apparent from the start, or even before. Founding father Jean Monnet said: “Europe’s nations should be guided towards the superstate without their people understanding what is happening. This can be accomplished by successive steps, each disguised as having an economic purpose, but which will eventually and irreversibly lead to federation.” The current Commission President Junker follows the master (“When it becomes serious, you have to lie“) and also asserts that “There can be no democratic choice against the European treaties.” Disguise, deceit and denial are deeply embedded in the EU’s genes yet Remainers seem not to care (see There’s None So Blind).
Literary analyses often mention the phrase ‘A fish rots from the head down’ as the likely inspiration for Marcellus’s comment, by which he is implying that the nation’s problems start at the top of the political hierarchy. The images of Tusk and Junker smirking each time they get something over Theresa May, and even leaders of minnows like Malta belittle her (and us), show clearly what they mean by ‘European values’.
Ever Closer Union is not an evolution of people willingly coming together to share more, it is a relentless power-grab by the centre and another arena for selfish, nationalist struggles. Much of the EU’s self-publicity is an inversion of the truth. For example, ‘subsidiarity’ is spoken of while the reverse is enacted,  peace is a proclaimed objective yet renewed conflict in Ireland is risked for political advantage , . There are many more examples listed in our semi-satirical Brexicon posts and in Brexit – a Brief Summary.
 More is Less: Subsidiarity (1 & 2)
 All I want is peace. Peace! Peace!