Not necessary, because the concept of “moral responsibility” is irrelevant to the argument. The argument concerns why someone acts immorally — is it because of ignorance of consequences? This is a separate issue from who can or can’t be held morally responsible.

This reverses a relationship we know from the premises. We know that an action that harms others (immoral actions) eventually harms those who perform it. But the author doesn’t think that implies actions that harm oneself must also harm others. There can be some actions that harm oneself that don’t harm other people.

Not necessary, because the author isn’t committed to the idea that there is anyone out there who must have a character defect. The argument is that those who commit immoral actions are doing so because they don’t know about some of the actions’ consequences. These people may or may not have a character defect, but the reason they’re doing an immoral action is not because of the character defect.

Necessary, because if it were not true — if people who act immorally intend the harm to themselves that comes from acting immorally — then we have no reason to think these people are ignorant of the consequences of immoral actions. If they want to hurt themselves from their immoral actions, then that implies they actually are aware that they’ll hurt themselves.

(E) means that everyone who knowingly harms themselves has a character defect. This isn’t necessary, because the author isn’t committed to the idea that there is anyone out there who must have a character defect. The argument is that those who commit immoral actions are doing so because they don’t know about some of the actions’ consequences. These people may or may not have a character defect, but the reason they’re doing an immoral action is not because of the character defect.