Initialisms Are Not Acronyms

Brett Kelly explains The Common English Mistake You Desperately Need to Stop Making:

Please stop referring to initialisms as acronyms. The longer this goes on, the more likely it is that the definition of “acronym” will be amended to include initialisms. If you don’t think the English language is above accepting glaring errors into the canonical language based purely on widespread, extended usage by regular people, I’d like you to meet my mortal enemy, “irregardless.”