You are correct in that it is difficult to find an unbiased evaluation of any 'political' person. There are those who hate the person and those who love him. Finding a middle ground author is difficult.
And then again, are the "...diaries" about him as a young man? What he became later is the facet I see most. His travels thru South America, especially in the level of some of the disadvantaged, read poverty stricken, would undoubtedly uncover some tragic circumstances. Same as here, in the deep South and on the Reservations. Is he another rich kid with a guilt complex?
I know of some of the atrocities committed by the BIA and some of the Settlers and various Church societies in this country. I know little of the South American parallels. What I know of the Franciscans and the Jesuits and their methods competition for souls and the enrichment of their societies would lead to tragedies untold. The 'Church', via some noble ones have a history of supporting the Campesinos and Indian tribes, on the other hand, the 'Church' heirarchy has always supported the aristocrats or landed gentry and helped to maintain their position of dominance in ruling the various countries.
It seems there are two or three alternatives for the governance of a South American or Central American country. A military junta, a dictatorship, no matter what he might call it, as in Castro or Chavez, and an elected leader and party. The last alternative is the rarest.
Kool aid time.