A months-old blog post written by a respected medieval scholar, Allen J. Frantzen, has gained a second life on social media — and whipped the discipline into a frenzy.

The post, entitled "How to Fight Your Way Out of the Feminist Fog" and published on Mr. Frantzen’s personal website, attacks feminism, alluding repeatedly to "anti-male" propaganda, paints men as victims, and offers advice on how they should "clear the fog." Mr. Frantzen retired in 2014, after more than 35 years at Loyola University Chicago.

The post borrows terminology often associated with men’s-rights activism, including encouragement for men to take the "red pill" of reality, not the "blue pill" of illusion, and to break away from the feminist fog. The fog, Mr. Frantzen explains, represents how feminism hangs over society — in a "sour mix of victimization and privilege" — and intimidates men into accepting its perspective.

Medieval scholars have widely condemned the post online as misogynistic, under the hashtag #femfog.

That reaction has also taken the form of blog-post rebuttals, along with lighthearted memesmocking the idea that a feminist fog is gripping society. For many in the small, close-knit field, though, Mr. Frantzen’s comments were an unwelcome window back to a time when medieval studies felt less open to women — and a reminder that discrimination persists.