Scott Lemieux once called this the "my-utopia-versus-your-grubby-reality asymmetry," a delightful turn of phrase which has stuck with me since I read it.

Although Lemieux was talking about something subtly different from, or possibly a subset of, what you're talking about: the practice of describing the benefits of your own preferences as if you could completely and down to the smallest detail redesign the relevant system from scratch, while insisting on subjecting your opponent's preferences to a rigorous "how do we get there from here" analysis with all the compromises, imperfections, and unforeseeable obstacles the real world always entails.