Under these terms, all 400+ tribes north of the deserts of North America were prehistoric until the arrival of the European and some paper.
This only sounds prepostrous if you don't understand what the terms mean.
This is also roughly the timeframe when the last stone-age society near Europe finally got subjugated by Europeans and stone age finally ended in the old world, when the Spanish crushed the Guanches in the Canaries.
It'd be really nice if all parts of the internet engaged in good faith debates on topics they were knowledgeable but finding that phrasing preposterous isn't unreasonable if you've spent a decent chunk of time exposed to reddit and twitter.
I agree that you're correct and reasonable, but I also agree that the person you're replying to was correct and reasonable when expressing caution over how things are worded.