I dunno... The notions that this man can opt out and then survive, to me, means that everyone should be able to opt out to survive, which is silly and an entitlement that no one in the raft should be privy to. The notion of treating another humanely went out the window as soon as straws were used to randomly determine who was going to die for the direct benefit of all parties. Either we're all in, or we don't do it, but that man's sacrifice will not be a cruel joke just because someone said 'no, I don't want to take the risk' and then said 'I want the reward anyways'.
I would like the man with the short straw to also decide how he dies, if he needs help, or can do it himself... but man, that is a hard scene...
In my opinion we're all going to have survivors guilt from this, along with possible other issues after the fact. We're eating a fellow person to survive.
What a cool question! I like pondering these.