I hate to say it but what the bloke apparently said seems only too true, i.e. killing OBL will simply martyr him in the eyes of many an extremist-in-the-waiting; and which surely, if taken to its logical conclusion, means we'd also better kill every one of his ten's of thousands of current followers too - uhm, and then we'd better kill all their brothers & cousins, lest they too coming looking for revenge..... so where / when do you stop, would you also kill this bloke, just in case ?!
In any event, based on what he said ( if that indeed was all he said ) , one might say that his punishment doesn't fit his crime.