It's harder to teach economics to a leftist than to find tolerance in a rightist. Most humans are innately tolerant, but there's no such thing as innate understanding of marginal utility, demand curves, consumer surplus, negative externalities, etc. It just seems easier to find rightists willing to let go of their fear of those who are different, than to find leftists willing to let go of their envy and resentment toward the rich and their paternalism toward the poor. Polling data on libertarians confirms what we all know about where they're found: http://libertarianmajority.net/libertarian-polling.
But if we are ever to become a majority, we have to try to balance our appeal to Left and Right. If that means trying harder to recruit from the Left than from the Right, so be it. As Starchild correctly complains, our movement far too often reaches for the low-hanging fruit of constituencies with an obvious self-interest in libertarianism: my guns, my dope, my taxes. We instead need to emphasize our environment, our children, and our communities. My favorite way to do that is through EcoLibertarianism: http://ecolibertarian.org/manifesto.