In response to a question about whether adopting a common fiat currency among multiple nations in the 1700s would cause inflation, an answer claimed that it happens all the time [today] and nothing happens.
In other words, the respondant is citing the consequence of a modern action or behavior to explain what he/she believes would be the consequence of the same or a similar action or behavior in the past.
My reaction was to believe the response was poorly researched, assumed facts not in evidence, what intrinsically false, etc., etc., etc....
And then my brain locked up because it wanted to describe the intrinsically false nature of the argument with a single word — but couldn't come up with one.
Is there one?
I tried "disingenuous," but that's almost an upside-down-and-backwards way of looking at it.
I tried fallacious, and it's close (and might be the appropriate word).
Obviously the phrase, "that's a bad assumption" would work, but I'm hoping there's a single word.
As an example sentence, my comment to the above respondant would be, "your statement is ___________."