You don't necessarily know what population was the largest either. Most of the history of the "Native" Americans is word of mouth, rather than actual written/documented history. There are Caucasoid remains from coast to coast, and they're all far older than any American Indian (far better term for them) remains we've found to date, by several thousand years: Kennewick Man, the mummies down south, the settlements on the east coast, and so on. So, no, the American Indians weren't the only people here, and they very well may not have been the largest population -- and, besides, in one of the largest DNA samplings of American Indians to date (a Mormon was trying to prove they're Jewish), it was shown that more than 80% of them had European influence in their blood. What about that? :P
-- Keep in mind, they were all "pure" Indians.
Well, the term "native" implies they originated from America, which they didn't. They're Mongols who migrated over and settled a large area of the continent (though, the settlements were far and few between, nothing like we have now). By that same thought, we can call the Nordic peoples who came over native too, 'cause they lived here too, right?
There's being logical, then there's getting upset because someone called you out on your little attempts to teach people the wrong history. Don't get upset because not everyone follows your Liberal ideologies. ^^
