Art by monsters is not indispensable. There are so many artists who AREN'T serial rapists (or raging homophobes, or unrepentant transmisogynists, or men who sexually assaulted their colleagues on the goddamn Hugo Award stage, take your pick), that those of us who decide to eschew a monsters' work are not missing out on nearly as much as one might think.
And nostalgia for stories whose author turned out to be a monster wouldn't justify insisting on those stories' essential literary canonicity.