The concept of human rights started forming in 1715ish and was caused by the Enlightenment. Of course, it took a while for these things to take root, and it grew throughout the century as philosophers debated on what it meant to have human rights. It's not that human rights don't exist, it's just that nobody had even considered that human rights might exist in the first place. It was a foreign concept that ended up with the US declaring independence and many wars in Europe against the monarchs. The freeing of the slaves came later, because of many deep rooted expectations and such. Considering that the freeing of slaves happened quite soon after (except in confederate states), people were quite quick to realize that African slaves were people too. Slavery in the US was fairly quickly abolished in many of the states, and then in order to get the confederates to stop they had to bypass the 10th amendment that limits the federal government's power. And that little civil war... almost forgot that...
The thing is, the day America died was the day that the Union armies trampled all over the confederate states' right to rule themselves.
This argument is based on the idea of private property, and I'm sorry, in order to actually own previously unowned land, you have to work and improve the land and stay on it, which most tribes did not do. They moved around, forfeiting any land they could have owned. Some actually stayed in one spot and I really disagree with them being taken out, but many of the other tribes had no land that could be taken at all.