Musing about Artistes

When I read about Arthur Miller dying, I remember that my first thought was:  “Well, poor Marilyn must be tap-dancing to the front gates and back again!“  He treated her pretty badly, including writing a scathing and cruel memoir after her death. 

So my question is this: When does brilliance trump being overbearing and hubristic? And should it? Yes, Miller was a brilliant writer. Just as Picasso was a brilliant artist and Byron was a brilliant poet. But they could all be notoriously hateful and selfish to people in their immediate intimate circle. (Byron was lionized when he was at the height of his ill-tempered outbursts and antisocial antics in the European salons, and still women swooned at his feet, petulance notwithstanding.)

There are countless other examples of writers, poets, painters, musicians, sculptors, etc. who treated their loved ones abominably and acted like selfish high-strung children, and yet they're lauded and revered for their accomplishments. (Don't get me wrong—for the most part I'm standing shoulder to shoulder, lauding and revering with the best of them, guilty of the same oversights.)

Unkempt and ill-bathed, prone to moodiness and fits of temper, so self-absorbed he would sell paintings to friends for cash and steal them back when he got half the chance, Soutine was a difficult character. But the power of his genius made him enormously attractive and he was rarely without a patron.

So why do we let "artistes" get away with things we wouldn't dream of indulging in the average husband, wife, lover or friend?  Is it just a privilege of being a genius? And an occupational hazard for the people around them?