Let's just say, we simply disagree.
There are Democrats who are definitely small-r Republicans and most Republicans would probably consider themselves small-d democrats, so your analogy breaks down there.
I don't believe it breaks down completely, specifically because, I don't agree with your evaluation of republicans and democrats. It's obvious you don't see much difference in the two parties and little differences between the positions of individual members.
However, this isn't about what interpretive values you may place on someones political affliations. That's highly subjective. This is about what the individual believes and professes. That's the whole point of this exercise into political awareness.
Secondly, libertarianism is a political ideology, like liberalism or conservatism (although it is not completely exclusive of those labels - there are left-libertarians and right-libertarians). It is not simply the creed of a political party. The Libertarian Party exists, ostensibly at least, to promote libertarianism, but libertarianism doesn't exist to promote the Libertarian Party. In fact, libertarianism as a body of thought considerably predates the LP. So your analogy is a little bit like saying that a conservative should belong to something called the Conservative Party rather than the Republican Party.
I hear you, but... Look, you can interpret anything in life, any way you want. In regards to politics, I can't help it, if you're adverse to politcal association and labeling. That's life. While eveyone can't be stuffed into a certain political reality, 100% of the time, there are some realities that we all must face. While political philosophies and ideologies, don't always jive with the individual party agenda, on every issue, it's still proper to make such political connections and links.
In the bigger context of communications, historical precedents are one thing, but we are living in the 21st century. It's pretty clear to me, that most republicans, folow the Republican Party agenda/platform and most democrats follow the Democratic Party agenda/platform. I can't and won't exclude the fact, that most libertarians, follow the Libertarian Party agenda/platform. Until you can prove me wrong, I think its fair to rationalize politics in this manner. If people get so upset with political labels, they should call themselves independents and leave it at that. I think some folks, like the convenience of political parties and philosophies, when it suits a certain situation, they might find themselves in the middle of, but easily cast off, such associations, when they feel its not so acceptable.
And if there was a ground swell for a true, a real, national conservative party, I'd seriously consider joining it. But as long as the Republican Party remains the home of the conservative movement in America, I'll remain, a republican, in the Republican Party.
For an advocate of individual liberty and limited government to decide that it makes more sense to work within the Republican Party than the Libertarian Party is no different than a person making a decision that one can work more effectively for environmentalism within the Democratic Party than in the Green Party.