Well, I don't know whose responsibility is, but I'll tell you the whole problem.
I only have one player, and we've been playing for a while together; I live in a country where role playing is very uncommon, and I feel a little awkward when I play with people older than me (I'm 21). The only player I have has my age and though we get along well, we have the tendency to invest our values and morals in our role playing games.
He's a very explosive guy and the kind of person that blames the GM and flips a table when his character is below 10% health. It's quite difficult to create challenges and traps for someone that takes it so seriously as to basically want to punch you.
Last night, we were making a character for a new game. His race is known as "demikin", a demon-like humanoids who have no feelings towards strangers, thus they are able to kill without feeling any sort of joy or remorse. In Savage Worlds terms, the race has the Bloodthirsty hindrance, and since they don't really value life the only outcome of conflict they know is killing. With his other starting hindrance choices he decided to make him more violent and have a worse attitude by adding Heartless, so he could be sadistic when killing enemies.
I am a very... sensible kind of GM, and I'm not saying that's a good thing... I have a tendency to act on injustice, and when a character does something like stealing or killing I actively seek to punish them until they learn their lesson. I'm capable of focusing a whole story session on guards pursuing them for miles, or on the gods taking something away from a character. I just can't stand characters who try to look "badass" by being villainous and sadistic, and that's something I've told my player before; being the only player I have it's tough to participate in the adventures of a guy that laughs when he shoots a bandit in the head while they're begging for mercy. Plus he expects his PC to have an almost comical romantic life without his attitude getting on the way. He's the kind of player who wants to do things without consequences, and the fact that when his characters are about to die he goes berserk made me realize letting him pick that race was a mistake.
I told him that I had the tendency to be a little excited with the pursuit of justice, and that if I ever became "power mad" he should kindly let me know. Then he frowned and said he'd change the hindrance, in a bad way... I started explaining why I thought a violent character was a problem and he exploded again, saying stuff as "Thanks for ruining my whole night" or "you're guilty of making me so angry".
So I've been thinking... was it really my fault? Or is it him?
In any case, what should I do? Should I just give up on playing with him and find a website where I can find roleplayers around my age?