Like user Snca said, Mexicans are generally a hybrid of European and Native American etc...and thus are not indigenous.

Also for the most part, all land was "stolen" from someone else throughout history. Native Americans mercilessly murdered each other in huge wars in order to steal their enemies lands/hunting grounds, long before Euros showed up. https://en.wikipedia.org/wiki/War_Before_Civilization

It doesn't actually make any real difference that Euros did the exact same thing by capturing their disputed land. Unless you think the color of their skin for some reason made it more of a moral transgression.

It feels that you're viewpoints on these subjects tend to be shallow. Read some history and anthropology to learn about the world around you!