what is so special about the program which makes up a human, that it would be morally wrong to shut off the program?
We haven't figured out how to turn it back on again. Once we do, maybe it will become morally ok to turn people off.
Because people are really annoying, but we need to be able to live with each other.
We need strong inhibitions against killing each other-- there are exceptions (self-defense, war), but it's a big win if we can pretty much trust each other not to be deadly.
We'd be a lot more cautious about turning off computers if they could turn us off in response.
None of this is to deny that turning off a computer is temporary and turning off a human isn't. Note that people are more inhibited about destroying computers (though much less so than about killing people) than they are about turning computers off.
You all know the rules: