I think I get the basic idea behind the whole sub-self thing. One sub-self wants to eat the cake and another wants us to live a long healthy life. Unfortunately the cake eater often seems to carry more weight than the boring health freak, so the cake eater is an evil tyrant destroying the health freaks liberty.
We all have these inner conflicts; one of my sub-selves is a shoplifter and I deny his freedom every time I walk into Exclusive Books or Incredible Connection (of course if I didn’t someone else probably would). Some people don’t do this even though they know they should; they are bad. But some people simply can’t deny this sub-self what it wants, these people are mentally defective (in this case kleptomaniacs); they are not “bad” (though I still wouldn’t want these people in any shop of mine). Many libertarians don’t mind restricting the liberty of the insane.
That’s my take on the sub-self argument for paternalism (and the destroyer of libertarianism); that we should restrict the freedom of the insane.
If you follow this link, you'll find a blizzard of fancy terms backing up sub-self theory (this time without spelling errors so bad that even I spotted them). There is an excellent chance that I don’t understand it all, fortunately this is not my fault it is just a renegade sub-self.