An apologia is a defense especially of one's opinions, position, or actions.

// The opinion piece reads like an apologia for the industry's reckless behavior.

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"Yes, Barbie is a polarizing toy ... but [Greta] Gerwig leaped right to what else Barbie is: a potent, complicated, contradictory symbol that stands near the center of a decades-long and still-running argument about how to be a woman. ... The movie is a celebration of Barbie and a subterranean apologia for Barbie." — Willa Paskin, The New York Times, 11 July 2023

As you might expect, apologia is a close relative of apology. Both words come from Late Latin; apologia came to English as a direct borrowing while apology traveled through Middle French. The Latin apologia can be traced back to the Greek verb apologeîsthai, meaning "to speak in defense; defend oneself." In their earliest English uses, apologia and apology meant basically the same thing: a formal defense or justification of one's actions or opinions. Nowadays, however, the two are distinct. The modern apology generally involves an admission of wrongdoing and an expression of regret for past actions, while an apologia typically focuses on explaining, justifying, or making clear the grounds for some course of action, belief, or position.