This little tidbit was spotted on BuzzFeed.
Okay, here’s the deal. When you mean “a comprehensive and fundamental law, doctrine, or assumption,” “a primary source,” or “an underlying faculty or endowment” (M-W), then the word you want is principle. When you mean “a person who has controlling authority or is in a leading position” (M-W), such as the person who has the power to put you in detention until the day you graduate from high school, then the word you want is principal. In this case, although Allen Gregory may very well love his principles, what they meant to show was that Allen Gregory loves his principal.
In principle, the proofreader of this article might want to make checking for spelling of principal importance.
Bonus MRP moment: In addition to this delicious typo, BuzzFeed also brings us “14 Punctuation Marks That You Never Knew Existed.” Impress your friends and scare your enemies with your new knowledge of guillemets, sheffer strokes, and asterisms.