What do you call the opposite of a libertarian?

[FEMA Camp Administrator]

"Communitarian" is the appropriate term when comparing nuts-and-bolts policy and philosophy, I would imagine. "Authoritarian" sounds, as Goldwater described, biased, and stresses the ridiculous one-dimensional dichotomy that libertarians (and the liberal right in the West) would have us unquestionably embrace.

In general that would be a populist.

Absolute monarchy wasn’t populist.

Both statements are unnecessary.

Populism is a political style, rather than a coherent set of political stances. Reagan, for example, was a populist, as were his rhetorical idols and political antitheses FDR and Truman.

Monarchy wasn't necessarily communitarian. While monarchies emerged prior to what we call modern capitalism, they at that point upheld feudalism, which is generally irrelevant to contemporary political discourse. It's not beyond imagination (or personal experience) to hear libertarians argue in favor of a monarchy or some other undemocratic government structure (talk to John Dule or, for older folks here, wormyguy). "Libertarianism" is not simple small-l classical liberalism for that reason (among others). While it might be appropriate to generally place monarchy (in the traditional, European, pre-1848 sense) under "authoritarian right" in our little picture-based political matrix memes, it would be inappropriate to juxtapose it as the opposite of libertarian since then we're comparing apples and oranges.

[FEMA Camp Administrator]

Authoritarian, which is why I'm always so confused when the politically illiterate conflate libertarians with the alt-right.

You yourself are evidence of the generally odd association people make between libertarianism and the far right. You're uncomfortable with democracy since it allows others to vote on what happens to your things. But this stems from a few other sources as well (see below).

1. The more generalizable reason for this conflation is the resort to authoritarianism as the last stand against communism. There are reasons for this, of course, and sometimes good reasons (capitalist development, even authoritarian capitalist development, leading to better long-term outcomes than that seen in big-C Communist societies), but for whatever reason hardline capitalist libertarianism is seen as a step away from fascism. (I recall some Internet picture showing a YouTuber's evolution from diehard libertarian/ancap to fascist, with the presumed outside pressure being the existence and perceived threat of Internet communists)
2. The fact that the "Ron Paul" crowd of 2012 essentially melted away and (per the popular narrative) a number of former Paul supporters were in the Trump camp. Sanchez himself is a good example.
3. The fetishization of Constitutional liberties can lead to a strident opposition to efforts to "impose" any other "liberties" (for example, Goldwater's opposition to the CRA on constitutional grounds). One of the many battlefields for this is over the legacy of the CSA and the American Civil War, but there is also opposition to modern-day social engineering, which is a key source of angst (so we are told) of the "alt-right" (think hatred for feminism).

[FEMA Camp Administrator]

The most logical term would be "authoritarian" since authority is more nearly an opposite of liberty than community is.   One may take a libertarian position for communitarian reasons, or have a communitarian account of what a more libertarian society could look like.  One may support an expansive, interventionist government for Hobbesian reasons, rather than any belief in a substantive, organic community. 

I would disagree with this on the grounds that "authoritarian" is usually used to refer to a political system (i.e. "monarchy", "democracy", "dictatorship") rather than a set of political or social positions (abortion, taxes, environment). While the political economy of authoritarian regimes tends to gravitate towards state-led solutions, this is not a necessary component of such. I can see both "collectivist" and "statist" being more appropriate terms (albeit, perhaps more extreme than "communitarian").

[FEMA Camp Administrator]

The opposite of a libertarian is someone who wants to micromanage how you conduct your personal life, all while taxing you for the privilege. So the semantics of it don't really matter; the opposite of a libertarian is just a bad person.

Nah.