You´re being too harsh on this show.
You´re working under the assumption of "virtual world = real life". Sakamoto is simply showing to us how wrong that is. Yes, you have these other characters already mercilessly fighting each other to death, but if I may make an assumption myself: As someone who´s used to a gaming environment to the extent of his, the notion of doing the same in real life is MORE unreal than to a person that never or only casually played the game.
Imagine you´re an experienced Team Fortress 2-player. Suddenly, you´re on an island and someone told you "kill each other to win!". What to you do? I hope I can speak for all of us when I reply that question with "Are you friggin kidding?!"
We´d be quick to draw the conclusion that playing TF2 irl would be a VERY bad idea.
Now, what would a less experienced TF2-player or a complete newbie think? Well, at least I´d guess he/she would be less thoughtful about possible consequences and, without deeper knowledge about the circumstances, be scared enough to just pull the trigger on anything that moves.
To make it short: Sakamoto is in a stage of denial, disbelief and confusion. Most of his "enemies" are not, because they can´t make the clear cut between game and reality as Sakamoto is capable of, strange as it may sound.