What was Twain's attitude toward racism and slavery?

Mark Twain opposed slavery and racism. Many of his works point out the absurdity of believing one human being is 'inferior' to another even in the face of overwhelming evidence to the contrary. He also took slavery out of context, comparing it to other periods in history or scientific knowledge to show how the system was built on a shared delusion of Americans during the time period and not a universal aspect of civilization or of the mind.

I think it is easy to be confused by the language used by Twain, but I believe if one looks at the whole of his writing, it is clear that he used dialect as both a personal trademark and a way to get people to see themselves in satires which openly critiqued society and human nature. To me, the main proof that Twain opposed slavery is in his later work, in which the hope of changing people's minds is no longer present and he reveals deep feelings of personal failure and hopelessness in both himself and the human race.