Of course Sam Clemens was a racist.  He was also a Darwinist in the best 
tradition of Herbert Spenser. Darwinism, which has little to do with 
Charles Darwin, provides the “scientific” underpining for racist  
beliefs.  The “survival of the fittest” paradigm leads directly to the 
imperialism Sam eventually came to criticize.  It is also the 
justification for liebensraum. We see in Clemens through the years 
increasing enlightenment – never fully attained. Any difficulties 
Clemens may have had with “Blacks” is dwarfed by his attitude towards 
aboriginal peoples, especially the American Indian.  I’ve been reading 
Kerry Driscoll’s book, Mark Twain Among the Indians and other Indigenous 
Peoples.  She paints an amazingly detailed picture of Sam continually 
running into the contradictions and difficulties that come from his 
racist/darwinist mindset. Adventures of Huckleberry Finn may give us a 
glimpse of some emerging enlightenment within Mark Twain but it would 
still be many years yet for him to accept the idea that “Indigenous 
People” may in fact be human.  Sam was willing to accept the American 
negro – because he grew up with them.  I doubt he would have wanted his 
daughters to marry one, though. For myself, I believe that anyone who 
thinks “races“ are anything more than cultural constructs is a racist.  
Thinking that the “other” is perhaps treated unfairly does not excuse a 
person – they are still racist.