The question I have been thinking on lately is when does a change requested by an editor equate to being a poison pill?

What I mean is, when do the changes requested by an editor go too far and require a writer to pull a piece from consideration? I haven't really had this situation come up with my fiction, but certainly have gotten into some heated arguments with others on rare occassions regarding nonfictin pieces. Generally this has been because an editor wanted to alter something to be inaccurate or substantively alter the intent and idea(s) behind the piece.

Fortunately, this has been rare, but I have wondered what and where the line is for others and if they have had to pull a piece. It seems to me that it would be an especially brave or foolhardy thing to do depending on the reasoning and the stature of the publication. For example, if the Paris Review wants to alter something to better suit the tastes of their readers I think it is foolhardy to resist. On the other hand, if the change substantively ruins the piece or markedly changes it so that it reflects poorly on the author's skills and intent, then I think it would be a brave thing to do.