I’m not sure who came up with it, but the first time I saw it was at the blog Vox Populi. Originally from an Onion video, the phrase, “the train is fine”, provides a fine retort to dealing the rhetorical types who… well, wait, read this:
It may help to keep in mind that whenever you try to use information to persuade a rhetoric speaker, you sound like “the train is fine” guy. You may be correct, but you’re totally missing the point.
The usage has now evolved to be used offensively:
“[...] the train is fine” is not utilized simply as a means of needling those with whom one disagrees. It is utilized as a rhetorical means of demonstrating that the person with whom one disagrees is focused on the wrong thing, often to the point of seeming obsession. In other words, the behavior is observably similar to that of an autistic person, which is why the application of the phrase is funny. Humor is contextual, after all.