I don't know enough about El Salvador's politics to know whether the mass imprisoning brought down the gang murders and improved stuff on the street, but why, once you've got people trapped and unable to do harm, can't you go back through them using officials you audit for gang influence or whatever and have individual trials? Instead, they did a farcical hundred-person-at-a-time show trial for the people they imprisoned, so who knows what portion were guilty. What it makes clear to me is that there's no interest here in identifying the innocent or guilty, but plenty of interest in keeping the undistinguished mix caged up like dogs in a kennel for the rest of their lives. What excuses do you make for that?