Nationalism is part of the bedrock of all nation states. It could be argued that attempts to suppress such ideologies have been shown to be futile when the authoritarianism that imposed the suppression was weakened. The collapse of the USSR and the fragmentation of the former Jugoslavia are just two examples. The resulting conflicts were disastrous.
Like the steam from a boiling kettle finding an outlet in the spout or the power derived from steam engines large and small being usefully directed the phrase "let off steam" has become a pithy way of describing excess to be dissipated as eg the parliamentary assemblies in Scotland and Wales have, so far, allowed their civil societies to function with those for or against full independence being able to join together co-operatively.
It`s all very well for Mr Junckers to spit fire and brimstone at Poland and Austria but if Marine Le Pen becomes the next French president I doubt she would bend to his tirades. Nationalism is part of the living breathing nation state. It functions beneath the surface everywhere and is kept under control by democratically elected governments. By attempting to throttle it the E.U. has presided over its biggest increase in popularity all over Europe since 1945. For that single reason I will be voting OUT on June 23rd.