KahanistLiberal,
Your points made are valid ones, "all things being equal", as they say in the world of academics. However, in the real world of politik, "justifiable" is defined as "whatever can be gotten away with" - strength succeed and the weak perish. Modern nations today just use a lot more "negotiating" and a lot less "invading" to achieve the same goals as before. In fact, some peoples and cultures we consider undeveloped today once almost did overtake Europe.
In the 3rd Century BCE, ancient King Asoka united virtually the entire Indian subcontinent under one Buddhist nation, and sent Buddhist missionaries as far into Europe as the Polish Court to "convert" the Christians to "the middle way" of Buddha. The Muslim Invasion which spread out of Arabia seized Jerusalem, vanquished the Byzantine Eastern Roman Empire, invaded western Europe across the entire continent from Romania to the Gates of Vienna and into France, after seizing the former Roman provinces of northern Africa and setting up a kingdom in Spain. Only military force checked their advance and "saved" all of Europe from Islam. The African Negroes might be the only racial group which throughout history only warred among itself and did not look outside of Africa with the intention of achieving wealth and building empires. And if this remains true today, it more likely is due to the Negros' never having achieved any intellectual or technological advancement which would have enabled it to compete successfully with other races and peoples. What can be stated with certainty is that the black Africans' lack of global conquest is not because of any special "sense of fair play" or because the Negro lacks the same aggressive, violent, and brutal nature of the Roman or Arab, but because the African Negroes never discovered the wheel and never developed the basic technology necessary to achieve a mechanized and disciplined society. All of Africa's modern nation states and cities we know today were built and modernized by British, Belgian, French, and German Colonial Imperialists, without whom the African Negro would still be a naked cannibal chased by lions and tigers. And which race/nation is the new colonizer and exploiter of the African sub-continent's resources? China!