@Deckard,
For many creative geniuses, their creativity may have been essential to their rejection of common values; one can understand that a unique view of the world might also include a unique (or at least uncommon) view of morality, and that a confidence in their vision as genuinely truthful could extend to their actions. Or to put it another way, if one lives an aesthetic mode of existence, then it may apply to one's morality as well; and, since art itself is amoral (or non-moral), so one's morality would be as well.
This may, however, be an exaggerated Romantic caricature of the artist as Hero. Rimbaud abandoned his poetry at, as I remember, the age of 19 and turned, or attempted to become petty bourgeoise; Nietzsche in private life was extremely polite to strangers, served in the Army, and sought marriage. Neither Goethe nor Wagner nor Joyce, while perhaps sexually promiscuous, were particularly known for advocating or practicing a different moral standard.