While researching images for signage at my current workplace, this image turned up from the Museum of Witchcraft blog here.
(It is no longer in public use, rather displayed in a corridor of their private library)
Although displaying an attitude you're unlikely to find advised in interpretation and exhibit labeling textbooks or courses, it sums up in a splendid way the conflict many of us may encounter in museums, and especially galleries staging controversial exhibitions - "If you thought it may be unsuitable for your children - WHY DID YOU BRING THEM IN HERE WITHOUT SCOPING IT OUT OR ASKING QUESTIONS FIRST?!!?"