Yes, extra judicial slaughter is wise isn't it? The ends justify the means. How very Machiavellian.
When their neighbors' biggest cities see deaths/year ratios comparable to that of Syrian mid-war cities (with Rio seeing more deaths/year than Aleppo itself), yes, it's very justifiable.
With a murder rate of 3 per 100000 Chile is the single safest south american country. 550 murders/year is their average recently. When compared to Colombia - the drug haven after Pinochet's kills - who has 24 per 100000 (8 times higher!), the murders/year in Chile would be comparable to 550 x 8 = 4400.
4400 - 550 = 3850 <--- numbers of murders/year avoided on the long run by the Pinochet government. The estimates suggest around 30k-40k people died due to Pinochet's actions. Assuming 40k:
40000/3850 = 10.3896103896
In little less than 10 years and 5 months, the deaths caused directly by Pinochet have saved the lives of the same amount of citizens. That, may I add, is in fact very pessimistic, since a good chunk of said deaths were, as mentioned before, actual criminals, some violent (murderers/rapists), some not as much (muggers), for Pinochet had a zero-tolerance policy towards criminals.
As harsh as it may seem, the constant fear and the eternally locked-down streets in many south american cities are an awful sight, the likes of which you're likely never going to experience; I can tell I'd rather have a maniacal dictator with severe death penalty over our current status and criminality.
Not to say Pinochet was a hero - he wasn't - but he did do something
to weaken the regional crime, which automatically puts him several levels ahead of most politicians down here.