It is not that a predator animal can create a hell out of the life of its pray that we are justified in doing the same as animal predators.
"In 1892, the Swiss Animal Protection Association launched a popular initiative against shechita. Although the Federal Council and the Federal Assembly moved to reject this initiative, it was accepted on 20th August 1893.
The Federal Constitution was then amended as follows by Article 25bis: ‘The slaughter of animals without prior stunning before the withdrawal of blood is prohibited without exception for every type of slaughter and every species of animal.’ "
Quote from http://www.swissjews.ch/en/religioeses/koscherfleisch/schaechtverbot.php)