Uh, wait a minute, hold on. You know libertarians that support gun control? That is really interesting, because I was almost certainly expecting the "Libertarians are a bunch of paramilitary reactionaries who want to keep their assault rifles and RPGs so they can form statewide white-power militias and oppress brown people" line. Seriously, libertarians supporting gun control is... fascinating. That pretty much flies right in the face of the whole "government shouldn't mandate to you what you can and cannot do" thing if you let government disarm people.
Civil rights legislation, depends. Libertarian political thought has as a central tenet the notion of looking at individuals as individuals, and granting rights as individuals, rather than to specific groups. So presumably there would be some minor level of disagreement with the more technical aspects of most race-oriented legislation, even legislation which clearly has very good intentions and is overall a very good thing for society. That said, this nuanced objection really should not be taken to mean that libertarians are anti-minority rights, because libertarians who actually genuinely follow their own principles should seek to correct situations wherein minorities are persecuted or denigrated to second-class citizenship for racial reasons - as such situations, again, grant (or really in this case remove) rights against a group, instead of individuals. I'm thinking that ultimately it would have to come down to opposition to the wordings of specific legislation instead of a blanket opposition to the legislation in general.
There is indeed a wing of libertarians who hold that fetuses are owed legal protection as human beings. I find the whole question of deciding at what point life begins to be a rather confusing one to sort out, and that I have trouble refuting on a moral basis such arguments, because the question seems extremely subjective. This is why, I think, the states' rights argument is popular for this question, because it gives communities a more direct influence over their own abortion policy, and since the question really doesn't seem to be very black-and-white at all, I can definitely understand reservations about enforcing a black-and-white federal policy. (That said, after sitting down with the issue a few weeks ago and again debating it last night, I find the resolution of Roe v. Wade to be a rather good solution to the abortion question on a federal level, so I guess I'm pretty solidly pro-choice.)
Gay marriage is another matter, and I've to admit it's somewhat disappointing watching my own libertarian acquaintances on the question. Some are rather devout Catholics who appeal to rather antiquated natural law philosophical arguments to defend the notion of 'traditional' marriage, and who want government out of the marriage question entirely. I find their philosophical basis pretty laughable, and while I empathize with the sentiment of saying government shouldn't be involved in marriage at all, it's not going away anytime soon. Personally I think that, as a contract between multiple individuals (generally two), government shouldn't meddle with restricting who should be allowed to enter into marriage. Provided that all parties involved can and do legally consent to entering the contract, I don't understand where government should have the authority to prevent certain such contracts from being made. Government's role is to enforce contracts which are made, not to mandate who can make them.
And while I know I certainly don't speak for all or even most libertarians, I can say from my own observations that we generally tend to be pro-marriage equality, pro-civil rights and anti-gun control, with abortion again being a mixed bag. Combined with drug and prostitution legalization, a non-interventionist foreign policy, and opposition to Constitutional overreaches like the PATRIOT Act or the NDAA, I think the label of "Republicans who want drugs legalized" is rather unrepresentative of our ideology.