That dictionary article is considerably shorter than this article, and by the way it uses the word "coup." The length of time over which the event occurred or Perrin's intentions are irrelevant. The event seems like an important one in Calvin's life. It states the facts, and helps the reader understand why all of the sudden the libertines are gone. As for the term "libertine;" "Christian," "Lutheran," and "Calvinist" were also originally pejoratives. We can't always use the terms a group prefers for themselves. You've admitted RSes use the term, so we should as well.