The survival of the survival lottery

In his paper 'The Survival Lottery' John Harris suggested that there could be situations where the rational thing to do would be to kill a healthy person and harvest his organs for transplantation, thereby saving several lives at the cost of one. Anne Maclean claims that such a proposal, far from being rational, does not qualify as a moral proposal at all since what it suggests is 'plain murder'. I argue that she is correct to claim that the proposal is not uniquely rational and that doctors could quite rationally reject it, but that she overreaches herself when she holds it not to be a moral proposal at all.