I was a registered Libertarian before I became a Dem. I have to say I'm still not enthusiastic about the Democratic party, really, except in as much as they're not the Republican party. The Republican Party is the antithesis of Libertarianism.
Government protection of the environment is a Libertarian position. Pollution denies individual choice and must be regulated to ensure that a majority does not force a minority to endured unwanted environmental damage.
Government protection of minorities is a Libertarian position. Those of us who want a free exchange of ideas require our neighbors to not stifle the free exchange of others. Government regulation is therefore required to ensure that one person's choices do not limit the options available to others.
I can understand Libertarians not wanting to associate with the Democrats, but it is contrary to every facet of the Libertarian ethos to associate with the Republican Party. A Libertarian Republican is an oxymoron.
As I see it, Libertarian philosophy is based around the idea that a free market driven entirely by consumers' and suppliers' best interests will produce the most prosperity for all. I buy into this as a basic idea - it works fine for, say, office furniture, more or less. But extending this same philosophy to the world of human behavior leads to absurdities like health care. The regulatory effects of supply and demand don't work in health care because most consumers don't know what they should "demand" without seeing a doctor to begin with, and because demand is frequently near infinite (if the choice is buying a drug or surgical procedure and death).
Similarly, in ordinary manufacture of widgets, looking only at the best interests of individual suppliers and consumers misses out on the interests of society at large. If I pour arsenic in my neighbor's backyard, he should be able to take me to court for destroying what's his. Similarly, if me and one hundred of my friends spread arsenic over much of the United States, that represents a very real cost. Neither I nor any one of my friends can be said to have destroyed one scrap of land or sea, but yet our cumulative weight will have done just that. That's a cost that is very real, very significant, and very unaddressable without intervention from an outside party.
I suppose the Libertarian party line is that a sufficiently informed consumer should be able to realize that it is not in his or her long-term best interests to patronize businesses that pollute the consumers' own environment with arsenic. I disagree for two reasons:
A) The many environemtal disasters that have befallen the world do not lead me to trust that this will work.
B) I do not see why I should have to endure arsenic in my backyard just because a couple million of my neighbors decide it's safe enough. I do not choose to be polluted with arsenic, not for any amount of money. I don't care who everyone else votes for, you're not going to convince me to allow it.
Therefore, the government needs to take the initiative to regulate business and industry so as to minimize and properly account for the costs of environmental pollution.
Government protection of sexual, racial, religious and other minorities is in the best interests of both the minorities and majorities. The economy flourishes when each person is allowed to activate their utmost potential. In our society, systemic bias has kept many minorities from achieving their maximum potential, and government regulation is required to reverse that effect.
What do the Libertarians have in common with Republicans?
*Republicans are opposed to some economic regulations (e.g. minimum wage), but not others (e.g. some agricultural subsidies). *Democratic are opposed to some economic regulations (e.g. some agriculture subsidies), but not others (e.g. minimum wage).
Republicans are opposed (just to name a few):
*to the right of a woman to control her own internal organs
*to the right of two adults to manipulate their external organs in certain combinations
*to the right of two adults to engage in certain contracts in certain combinations
*to the right of workers in places like the Northern Mariana Islands to choose not to engage in abortions, to not have sex for money, to freely seek the pursuit of happiness
*to the rights of the urban poor, suburbanites and others to not have their neighborhoods and bodies defiled by pollutants
*to the rights of 300 million Americans to not be stripped of their freedom without a fair trial and just cause
*to the rights of many millions of children and unborn Americans to not have to pay the taxes of the current generation
So, in conclusion, neither the Democrats or Republicans are truly Libertarian-friendly. The Republicans, however, are anti-Libertarian on social issues and anti-Libertarian on budgetary issues, and at best flaccidly lukewarm on economic issues. The Democrats are mostly good on social issues, better in practice on budgetary issues and at worst equivalent to the Republicans on economic issues.
The Democrats are the party that want to keep us free, from being polluted against our will, from being limited in our recreational pursuits, our romantic endeavors, our economic liberty, from our children being free to pay their own way, and not ours with interest.
And so that's why I consider myself a Libertarian Democrat.
*Update: I'm aware that this is more or less the same thing as the liberal-progressive philosophy. That's rather my point. Libertarians purport to represent the freedom of choice, and a number of them have been misled into thinking that a lack of government increases choice. It doesn't, and that's why the Republicans are not the best party for Libertarians who don't want to waste their vote. I'm aware that my positions are not the mainstream of Libertarian political thought - that's because part of the Libertarian message has been distorted.... IMHO. In any case, this is how Democrats can talk to Libertarians in a useful way, if nothing else.