I've never run across a petition aimed at stopping an author from writing something. And of course, such petitions would only even remotely work for very famous and established writers who are actually asked to disclose their plans for upcoming projects in advance. As a first time newbie author, no one (aside from a handful of people on writing forums and my nearest and dearest) have any idea what I'm working on, let alone whether it might offend someone.
But said famous author or script writer probably knows their demographic niche pretty well and would be unlikely to be dissuaded from a potentially profitable endeavor by a petition from people with opposing sociopolitical views.
It's not quite the same thing, either, to say one wishes that media that supports views they find objectionable (racism, sexism, homophobia, or on the other side of the sociopolitical spectrum, irreligiosity and the non-traditional family, say) would wither and die for lack of adherents and interest.
I have run across proposed media boycotts (on both sides of the political spectrum) of movies and books some people feel are offensive or harmful to some group or another. Boycotts aren't the same thing as censorship, because they're asking (not telling, unless coercion is used) people of a given mind set to use the free market and to exercise their right not to consume something.
They don't seem to work very often for books and movies, at least, because when someone makes a movie (Like the Last Temptation of Christ, for instance) that one group (that was probably not the movie's target demographic in the first place) boycotts, another group may well decide to see an otherwise "boring" movie to find out what all the fuss is about. It's an example of the old adage about the only bad publicity being no publicity.
