I most certainly have. I've read the novel, the mangas, and watched the movies. I thought that by now everyone would have realize that, given my constant postings of praise for the novel

.
And he wasn't psychotic, he was sociopathic. Sociopathy isn't a form of psychosis, but a supposed mental irregularity that causes a person to act in antisocial ways that usually involved harming other individuals either physically and mentally in order to feel excitement or a a kind of superiority.
As for him not being a villain, I do agree with you for two reasons:
1. Kazuo's condition was caused by an car accident that made him unable to feel any human emotion. Plus, nobody ever told him of the accident, so in a way, he's just an innocent person who had something dreadfully unfortunate happen to him and as a result did not know what he had to live for. That is, until he was placed in The Program.
2. Everyone was forced to kill one another anyway, so even if he had been "normal", he would have either been forced to kill others to survive, or die.
I suppose that he's just a villain in the traditional sense, since he does go after the other students and murder a great deal of them. Although, I don't really believe he
should be viewed as a villain given the circumstances of his situation.