Why did Mark Twain hate the concept of Imperialism?

Mark Twain believed strongly in the idea of democracy and
in the idea that people should be free.  You can see this sort of attitude revealed in
many of his books.  For example, in both A Connecticut Yankee in King Arthur's
Court aned The Adventures of Huckleberry Finn we see
Twain showing that he thinks that monarchy and elite rule are corrupt institutions.  He
shows that he believes that the common people should be give the chance to rule
themselves.  He clearly believes in the American way.

Twain
applied this way of thinking to his thought about imperialism.  He did want other
countries to become more like America.  However, he thought that imperialist countries
(including the US at the time) did not mean to try to actually improve the countries
that they took as part of their empires.  He thought that they, instead, were just
trying to exploit those countries.  This is why he opposed imperialism.  You can see
that idea in the following quote from the historywiz.org link
below

I said
to myself, here are a people who have suffered for three centuries. We can make them as
free as ourselves, give them a government and country of their own, put a miniature of
the American constitution afloat in the Pacific, start a brand new republic to take its
place among the free nations of the world. It seemed to me a great task to which we had
addressed ourselves.

But I have thought some more, since
then, and I have read carefully the treaty of Paris, and I have seen that we do not
intend to free, but to subjugate the people of the Philippines. We have gone there to
conquer, not to redeem.