You use a metaphor to describe some concept. The metaphor isn’t the thing you describe – it’s just a tool that you use. But someone takes the metaphor, and runs with it, making arguments that are built entirely on metaphor, but which bear no relation to the real underlying concept. And they believe that whatever conclusions they draw from the metaphor must, therefore, apply to the original concept.

You see the same problem constantly, in almost any kind of discussion which uses metaphors. There are chemistry cranks who take the metaphor of an electron orbiting an atomic nucleus like a planet orbits a sun, and use it to create some of the most insane arguments. The most extreme example of this in my experience was a guy back on usenet, who called himself Ludwig von Ludvig, then Ludwig Plutonium, and then Archimedes Plutonium. He went beyond the simple orbit stuff, and looked at diagrams in physics books of “electron clouds” around a nucleus. Since in the books, those clouds are made of dots, he decided that the electrons were really made up of a cloud of dots around the nucleus, and that our universe was actually a plutonium atom, where the dots in the picture were actually galaxies. There are physics bozos who do things like worry about the semi-dead cats. There are politicians who worry about new world orders, because of a stupid flowery metaphorical phrase that someone used in a speech 20 years ago. 

It’s amazing. But there’s really no limit to how incredibly, astonishingly stupid people can be. And the idea of an imperfect metaphor is, apparently, much too complicated for an awful lot of people.