There seems to be this idea embedded in human minds that there is a group of people who are just waiting to kill someone, and the fact that they have not yet found a way of doing it is the only thing preventing them from doing so. As soon as you show them that you can do it by hacking a pacemaker, they will go ahead and do it.

There is no shortage of methods of killing someone or inflicting bodily harm. As far as moral culpability, showing how a 0day exploit can be used to kill a person is akin to saying that you can use arsenic to kill grandma.