Many of my personal beliefs coincide with "libertarianism." However, I think this conversation highlights what I think are one of its flaws when applied to a large, pluralistic society like the US. You can't have any set of laws that all of the people will agree to. And, ultimately, you will have to force a certain sector of the population to abide by some laws.
Actually, a conversation about a pluralistic society should contain talk of fewer laws, rather than more which force people to behave in certain fashion.
Too many people see themselves as the "majority" (even when they're not, they often think they "should" be) and think they have everything right and want to force everyone else to do what they think is right. This often really screws everyone up because very rarely does a politician know what the hell to do to fix things. Too many political decisions are made from emotional decisions, because emotions are the one thing the majority of us have in common, and something that politicians can use to bend us.
We all hate to see someone starving on the street, therefore it is very important that Joe Smith over here get a group together to force everyone they know to cough up money for the poor guy starving in the street.
Of course, there are so many things tied up in where the starving guy came from to begin with and why he is starving. He may be a criminal, for all we know, who has robbed and killed his way into town but spent all his money before he ever got there and fell in the street there, a starving, deserved wreck.
He may be a saint that was nearly crucified in the previous town and just barely made it to "safety".
He may be a drunk who doesn't want to work, that now becomes a burden to everyone who is forced to support him.
But now we have two groups who think they know how to deal with this guy. The first one wants to pick him up, feed him and maybe give him some work. The second group wants to pick him up, beat him some more because they "know" he's a bad guy.
Given all the information that I laid out, you couldn't make a decision as to what to do with him if you were being honest about it and not reacting to your own, and everyone else's, prejudices. But both groups want to force everyone else to treat him the way they want everyone else to treat him.
So the NAP serves very well here. Why not let Joe Smith feed the guy if he feels like it should be done? In fact, if Joe Smith wants to feed him and get him up and working, why not get some other like-minded individuals together to help him accomplish that? It would actually make Joe Smith a pretty interesting guy that he is so concerned about the welfare of others, and in fact, if Joe Smith believes in a Christian God, he may well figure that he's helping himself earn a place at the right of his Lord by his righteous actions.
But if he leaves the guy in the street, dying, and works on getting everyone else forced to help the poor guy out - what does he accomplish? A lot of kilombo, a lot of bad feelings from those who don't want to help, and certainly no kudos from God for his Christian help (forcing others to do what you think should be done hardly counts as charity, after all). And hell, the guy could even die while Joe Smith is trying to get everyone organized!
And for the other guys who want to do the guy damage? Again - NAP. If anyone does anything against the guy, they are violating a basic tenet of Libertarianism. If he's lying on someone's property, that person has the right to move him. If the guy keeps coming back, the owner has the right to continue to move him. The owner can even get others to help deal with the guy in some other fashion (even locking him up until he promises to stop coming back). but he can't beat him, or kill him - it's not NAP. He can't keep him as a slave or prisoner without worrying about violating NAP and having the community come down on him as well.
This is all very simplified and out of this actually come private police forces and courts that people can subscribe to, and all of which have jurisdiction based on their clients (not necessarily location), and all of whom work together, etc, to provide order and justice.