It's not REPUBLICAN!!!! DEMONCHILD!!!! BEGONE!!!
That being said, they are missing one key point: libertarianism can be construed to support a lot of things, but ultimately, the anti-l's forget the most important factor in the equation - the individual. It comes down to the individual, and the individual's morality. Just because something is legal or accepted doesn't mean it's the "moral" or "American" thing to do. I'll give an example:
Libertarianism can be construed to support pedophilia, simply by virtue of the very free nature of libertarian ideology. On the other hand, anyone that thinks libertarians, such as myself, support pedophilia, are the most ignorant in the worst kind of way.
It's sad, really.