Sorry DMan, but the Sendero Luminoso wished to be responsible for the siege in the Japanese embassy back in 1996 (and beginning of 1997) because of all the publicity. However, it was the MRTA: Moviemento Revolutionario de Tupac Amaru, and the terrorists were executed without any form of trial.

First of all, don't get me wrong, I don't agree with their activities, but I can imagine why they use violence. uhmmm, let me phrase this different: I don't know what I would do if I was growing up and living up there in the Andes.
Violence is something you use when you run out of arguments before having said something. Normally. But what if you're not allowed to say something? What if, when you do say something that isn't positive about the government, get killed? What if your family members show clear signs of malnutrition? What if there's no good health security, education etc in your region of the country...???
I don't think there is a clear and firm line between "the good guys vs. the bad guys". It's easier to judge/misjudge(?) when sitting and relaxing with the prejudices in a comfi-chair in a rich First World country.

The actions by the Sendero Luminoso in the eighties did make a difference: e.g. there are more schools, vaccination programs, and villages get electricity. IIRC, the political actions of the Sendero Luminoso are in a dormant state, and "other" activities involve drug trafficking, and indeed, taking over villages in the selva (Tingo Maria and it's region).