This is colloquially known as the “nirvana fallacy”: the tendency to assume that there is a perfect solution to a problem. A politician who uses the nirvana fallacy gains an easy rhetorical advantage. He can paint inspiring pictures of his perfect world, and attack the existing state of affairs for not living up to it. He can accuse anyone who doesn’t accept its plausibility as cynical, lacking in vision, or principle.
But this advantage comes at a cost, because the nirvana fallacy makes you stupid. It stops you from doing the hard, gritty thinking about how to improve the world we have, since, faced with a series of complex, imperfect options, you overleap them to reach the sunlit uplands of an ideal scenario. Soon, you forget how to think about the real world at all. daqui, por acaso integrado num post sobre infra-estruturas de bicicleta, mas que podia perfeitamente ser aplicado ao pensamento de certos político e vocês sabem de quem é que eu estou a falar.