The comment you are replying to is embracing that complexity. Paving over it with simplistic thinking "Castro was evil and wrong" does a great deal of violence to the truth.

I am no fan of the shape Fidel Castro's Cuba took, but I think it is more important that we learn from the mistakes of the revolution (which are not a simple matter of being 'evil' or 'wrong') than that we demonize them.

In general, we should learn from history or be doomed to repeat it.