Dude, we have seen him crying because he had to endure it all without just lashing out... his classmates, the townsfolk, his friends... even the girls that are after him... the only characters that have been good to him without asking any in return are a bunch of undead...Pretty nice, though i must say i think he flipped a bit far given how he has been portrayed so far. Even if he became extremely mad i do not think he would go full murder hobo like that.
Everyone has given him problems one way or another... all for the possibility of going back home, and then this savior complex princess just says "ups, sorry we lied"... yep, called it!... this is a story on how they created a demon lord... i could bet that the first hero had something similar happening to them.
Holy self fulfilling prophecy!... finally or MC grows a spine!, not only tells it how it is to that dumb dumb, he offered several plans on how to manage what she wanted without calling kingdom ending entities to her world.
Although dull... i kind of get why the boney guy decided to stop the rise of the next demon lord.