re: What is the worst argument you've heard for a postion you support?

I'm a pretty strong libertarian, and I hear a lot of libertarian arguments being presented on the basis of natural rights by other libertarians, which is fine if they believe in a higher power or something like that, but when I hear the natural rights argument being presented on the basis of metaphysics or by someone who is an atheist, it really just sounds absurd to me. They have to make up reasons as to why we have rights and where we got them-- and it's just dumb.