Considering that this thread is about what is wrong with Libertarianism, and not Southack, I think that it would be a bit arrogant and insensitive for me to hijack this thread for a discussion of what I think that the general welfare clause means.
On the other hand, you'll notice that libertarians tend to think that the general welfare clause can be disregarded from our Constitution. They seem to usually claim that it conveys no power to government (i.e., has no meaning).
In fact, when you ask them, often they can't name a single thing that general welfare can mean. You libs really do read the Constitution as though those words were never written into law.
And that misinterpretation of our Constitution is ONE of the things wrong with Libertarians, per the topic of this thread.