The reactions remind me of a philosophy class I had, where the professor went for a thought experiment in order to explain an idea. "Imagine a world where ...". There was a physicist in the class who kept interrupting the professor, saying "well that's not possible because of how physics works". I would have asked him what he thought about Star Wars or The Lord of the Rings; could he enjoy them at all? But he ruined the class for me so I didn't :-).