If you read what I said again, you should notice that I’m not saying the data from 300 years ago should necessarily be used. I’m saying that the reason not to use it has nothing to do with people believing in dragons or unicorns.

The part about measurements is fair (they weren’t standardized at the time), but the rest is irrelevant. The decision of whether or not to use data should be on the basis of its scientific rigour and veracity, not the scientist’s beliefs.