Since, as you assert, gay marriage, drug legalization and abortion are not essential parts of what it means to be a libertarian - libertarians ought to be willing to concede these issues to conservatives.
If they are considered to be essential planks - then the libertarians are not going to concede either of these three.
Based on the posts so far - the libertarians seem very clear that abortion, gay marriage and drug legalization are all core principles.
Check out l4l.org. You could do with a lot of education yourself....
The crux of the abortion issue is human life. If unborn babies are human then libertarian philosophy is anti-abortion. Pro-abortion libertarians make the same arguments that pro-abortion Democrats make, that the unborn aren't really human.
Ironically the most hated libertarian on FR, Ron Paul, is anti-abortion.
Libertarians usually claim gay marriage is just a contract. This is a far more radical stand than that taken by liberals, who limit their ambition to giving homosexuals the right to marry each other and be subject to the same obligations and responsibilities as normal married couples, at least for now. The libertarian approach would immediately allow for polygamy and every other variation, as well as temporary "marriage" and prostitution.
Drug legalization, however, is the one issue where all libertarians agree. If they repealed all federal drug laws the next step would be to repeal all state drug laws, as well as any local regulations.
With pot this would have few negative side effects. Heroin, that's a horse of a different color.
The Libertarian view is entirely, essentially, a LEGAL view, not a moral view. In a pure Libertarian view, marriage and/or civil unions - and many other “social” issues, would not be a legal matter to begin with; the law would not be involved, either as a moral advocate for or against what Libertarians see are choices the individual must make within their own Liberty and by the moral view of their own conscience.
In the present environment that means accepting a legal remedy that is closer to the law NOT making a moral choice FOR us. It is not a position trying to promote a “moral” good; only what Libertarians believe is a more neutral LEGAL position; more neutral in the sense that the law becomes less the defining issue than our own conscience.