This is fine if everyone in the conversation has that same academic definition of pre-history - the problem is that bad actors will often latch onto that statement, ignore the definitions, and use that as a basis to argue that so-and-so people were sub-human.

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.