"The non-inflammatory antonym for 'libertarian' that you're looking for may be dirigiste."

Noted. (I had used the admittedly inflammatory "fascist.")

The OED defines "dirigisme" as "The policy of state direction and control in economic and social matters." Here are the examples, going back only to 1951:

1951 Archivum Linguisticum 3 220 Linguistic dirigisme, standards of correctness in a constantly evolving language.
1952 V. A. Demant Relig. & Decline of Capitalism iv. 94 These are but a few of the reasons for the increasing dirigisme of economic life on the part of the state.
1957 Times 26 Feb. 4/3 Their [Sinn Fein] programme is a strange amalgam of bombast, Chauvinism, and dirigism.
1967 New Scientist 9 Nov. 329/1 He warned his listeners against ‘too much dirigism’, reminding them of the USSR where crude political interference had forced men into politically neutral fields....

And for the adjective:

1957   Economist 12 Oct. 16/2   The French hope that the new community will pursue a ‘dirigiste’, or at least a Keynesian policy regulating and guiding investment on a European scale, and ensuring that the Germans do not upset the whole scheme by deflating too much.

I don't know. I'm feeling inflamed.

As long as I've got the old OED open — sorry I can't link to it — let's check out "fascist":

One of a body of Italian nationalists, which was organized in 1919 to oppose communism in Italy, and, as the partito nazionale fascista, under the leadership of Benito Mussolini (1883–1945), controlled that country from 1922 to 1943; also transf. applied to the members of similar organizations in other countries. Also, a person having Fascist sympathies or convictions; (loosely) a person of right-wing authoritarian views. Hence as adj., of, pertaining to, or characteristic of Fascism or Fascists.

The examples that go beyond the original reference to a self-proclaimed fascists seem to begin around 1960:

1960   S. M. Lipset Political Man v. 133   Fascist ideology, though antiliberal in its glorification of the state, has been similar to liberalism in its opposition to big business, trade-unions, and the socialist state....
1961   H. Thomas Spanish Civil War viii. 71   The Socialists..were described by [Communist] party jargon as ‘social fascists’.
1963   Times 27 Mar. 10/2   As the main body of demonstrators began to move away,..screams of ‘Fascist pigs’ and ‘Gestapoism’ continued.
1969   Times 17 Nov. 10/4   Taunts of ‘Sieg Heil’, ‘Fascists’, and the occasional smoke bomb from youthful demonstrators were bound to invite trouble.

The OED also notes a "Draft additions December 2005" definition:
depreciative. In extended use (with preceding modifying word): a person who advocates a particular viewpoint or practice in a manner perceived as intolerant or authoritarian. Cf. Fascism n. Additions, health fascist n. at health n. Additions. Recorded earliest in body fascist..."

1978   Business Week (Nexis) 22 May 10   Psychotherapy-as-recreation..has contributed in no small way to the kindred plagues of jogging and vegetarianism that are now so thoroughly disrupting wholesome social intercourse across our land. An acquaintance aptly dismisses such folk as ‘body fascists’.
1987   Courier-Mail (Brisbane) (Nexis) 10 Sept.,   Members of the NCC have been dubbed ‘green fascists’.
1997   Canad. Lawyer Jan. 46/2   It'll be fun to see what happens when the tobacco fascists run headlong into the human rights fascists.
1999   Independent 24 Mar. ii. 1/2   Now a half-naked male swigging Diet Coke and being ogled by stenographers in horn-rim specs is just as likely to upset gender fascists.

So it's like "soup nazi." Looking up "Nazi":

2... b. hyperbolically. A person who is perceived to be authoritarian, autocratic, or inflexible; one who seeks to impose his or her views upon others. Usu. derogatory.

1982   P. J. O'Rourke in Inquiry 15 Mar. 8/3   The Safety Nazis advocate gun control, vigorous exercise, and health foods.
1995   Independent 3 Nov. (Suppl.) 8/2   According to Hutchins, current fitness theory is peddled by ‘nazis’. Aerobics Nazis.
2000   Minx Aug. 71/2,   I learned to be more open and not such a Nazi in the studio.

Interesting use of "usu." When is it not derogatory to call someone a Nazi?