it should not be anyone else's responsability to take care of them
And why not? Just 'cause, right? Everyone is an island, and it's a zero-sum game!
You want to take survival of the fittest? Okay, you got it, along with all the crime, violence, back-stabbing, and other things people do in order to survive. Let's not forget that diseases are often contagious, and thus a social problem.
it takes smart people to make a Libertarian society work
Just like you? You can't even spell a common word properly.