The concepts of cloning a person or turning someone into a robot are historically viewed as unethical and morally wrong. That particular research is considered bad. No matter how idealistic he was about it at the start, even he notices the harm it does. And so, he sees himself as a fit sacrifice now, as he should.
Voicing something is wrong doesn't cancel out doing it anyways, that is why he needs redemption
Kizaru is really just standing around but ultimately doing nothing. He would need to do something very bad to be looked at as villainous or evil, but sadly so far this ain't it
He's a random side character, there won't be any time for something like that.