The main way in which the poem, "The White Man's Burden", justifies imperialism to the industrialized world and the unindustrialized world is that it implies that it is the "obligation" and duty of white men in developed and rich countries to colonies poorer countries--in order to implement more "modern" and prosperous forms of government.
All men were given the right to vote in the 15th amendment and the women in the blank amendment
The 19th Amendment
It was commissioned by Emperor Vespasian of the Flavian dynasty as a gift to the roman people.
What that meant was that they were looking forward to saving the Union itself more than saving the African-Americans. There were slave states that had not yet seceded and insulting them might cause them to leave. This is why they said that they were protecting the constitution, they wanted to keep territorial integrity and sovereignty, more than they wanted to free the slaves.