If it is dead, I would cut it unless it is a thin-branched deepwater. I like to leave those so long as algae doesn't grow over. They often die back in the wild and a well-known importer gave me that advice. It has turned out to be good advice based on my experience. If it is just bleached and the tissue is alive but devoid of zoanthellae then don't cut it but do try to lower the light level a bit to let it heal.