Define "stealing fair and square".
I will say that stealing "fair and square" was losing its legitimacy by about 1900. 10,000 years ago, "stealing fair and square" was quite honorable and continued to be honorable for thousands of years afterward.
Also, it's easy to say "stealing" is ok when one is the thief. If you are the victim, there is a greater tendency to say stealing is wrong.
"Stealing fair and square" is clearly documented through the end of World War I in 1918 when the Austro-Hungarian Empire shattered into smaller constituent countries.
The process of "Stealing fair and square" was ended by the United States of America after World War II wherein we insisted that we would not gain territory as a result of haveing crushed our enemies unconditionally. Of course, Russia was not keen to this idea, so please note in the margin of your text that they stole all of the Eastern Bloc countries, known as those behind the Iron Curtain. We may have disapproved of their imperialism but it happened and we could do nothing to stop it.
Note that the date was 1945. Note also that Israel was made out of whole cloth by stealing someone elses property to provide for the Hebrews.
Note also that Tibet and Kasmir and South Vietnam and other countries were "stolen fair and square" long after that.
Your assertion that "stealing fair and square" was losing its legitamacy by 1900, is unfounded. It has occured right up to the modern day, if you look at how the Abanian Muslims stole Kosovo from the Yugoslavs.
If by losing its legitamacy you mean to say that you approved of territorial conquest before 1900 but not after 1900, the I beg to differ. Territorial conquest, except as the result of national self-defense, has always been immoral as it results in the theft of sovereign land of one nation by another which has no political right to that land.
The entire point to my original post was simply, we took America away from the Indians and the Mexicans at a time when they were taking land from others. We may not have had a moral right to do so but it is done and so be it. I for one think I am better off.