Deluded: His beliefs are false and his ends therefore not reachable.
Noble: He means well and is courageous and kind wherever possible.
Fool: He behaves and speaks like a crazy person when his delusions are involved.

Also widely used by ordinary men to brandish idealists among them, who try to make some sort of better world: Ordinary men widely believe this is either not possible at all - everybody must be as immoral as they know themselves to be in real life, according to their own norms, or so ordinary men believe - or else only if the authorities agree. And ordinary men tend to be levellers: Nobody among them is allowed to be better than they are, for which reasons they consider deluded whomever does not share their prejudices.

Whence quixotic: Misguided idealist.