The writers REALLY screwed up Serrat when they had him execute a sailor. The only response that would satisfy the crew is to kill him. It would really be out of the captain's hands as I could see a dozen of the crew going up to Serrat's house (led by the COB) in the middle of the night and taking him out.
Everything since that point-of-no-return has made no sense. The guy is a threat they just ignore and they get bit in the ass every episode because of it.