"Well, I'm afraid it is Mr Slinkhard's opinion, and not yours, that matters within this classroom, Miss Granger."
--Dolores Umbridge (OP15).
Wilbert Slinkhard was the author of Defensive Magical Theory, a dull and heavily theoretical Defence against the Dark Arts textbook that favors more passive responses to dark forces (OP9, OP12, OP15, OP17, OP29). In chapter 15, Slinkhard claimed that counter-jinxes are improperly named, because he believed that “counter-jinx” was just a name given to jinxes to make them sound more acceptable (OP15).
Other canon notes and references
Hermione Granger disagreed with Slinkhard's assumption that jinxes are simply bad (OP15).