Hrmm... who's to say they'd hate Leon for protecting himself without any lethal damage? In my opinion, there'd be no reason to be angry at him if he had managed to protect himself without ending up killing Sayaka. In that same thought, I always did feel kinda sorry that was how things ended up how they in the game for him... Monokuma had refrained mentioning that killing in self-defense would still mark you as the blackened. There are ways to incapacitate an attacker without using lethal force, but it can be tricky to use such calculated movements when you are in an adrenaline-pumping fight for your life and are running on pure instinct of do or die.
In the alternate event that Chapter 1 had ended without any deaths and the class was able to determine that Sayaka had plotted the murder, Monokuma probably would have just laughed and watched the tension that ensues between all the students upon finding out that the seemingly innocent idol had been the first to have murderous thoughts. What if they tied Sayaka up?!
I bet had Sayaka lived, foolish Naegi would still be in denial she was capable of attempting murder... Naive child...