They would not apply the same rules to anyone else guilty of his crimes. It's an Alinsky principle: force your opposition to play by his own rules, but don't waste your time doing that yourself. Second, he was Asian, and racism against Asians - especially successful Asians - motivates more then just the Leftists in Peru.
Eventually Peru will descend into the madness that Fujimori staved off for a few moments in its history. Handing over the government to the indigeanos will result in bloody regression to an animist past, the end point of which will probably be takeover and domination by a patron tyrant state like China.
The question is, will the U.S. stand by and watch?
The people whose lives he saved know the truth about Fujimori. It breaks my heart that the bad guys are winning again.