Torture (to stick to the topic) shown on TV
. This indeed reminds me of Odai Hussein who probably enjoyed to watch bodies bending from electrical shocks while having some beer and a cigar.
No, you would not prevent potential murders from killing for fear of being tortured. The only result would be a brutalized public, thus leading to an increase in violence.
The death penalty in the U.S. (pardon this shift) exist, because people want revenge. There is hardly a politican or attorny left who believes in the deterrence of the death penalty. Same would go for torture.
Typically enough, you mentioned the French revolution, where people became more and more used to public executions and finally demanded to see more. The whole situation turned into a "panem et circensem"-thing which has had nothing to do with a proper legal system.