Yes, Che was ruthless and fanatical and sometimes murderous. But was he a murderer? No, not in the sense of a serial killer or gangland assassin. He was one of those rare people who are prepared to push past ethical constraints, even their own conscience, and bring about a greater good by doing terrible things.
Whether morally justifiable or not, there is something admirable in that — pure principle in a world of shabby compromise. Maybe this is why Che remains such an icon, both in image and idea.