Is it appropriate to dismiss from consideration an answer that mixes book canon with movie canon? The reason I ask is I just looked over an answer to a question of mine and the user answering had used a quote from Harry Potter and the Deathly Hallows Part 2 (film), that does not appear in the book, as part of her argument (for lack of a better word). In this instance (and perhaps this isn't a great example, but it's the only one I can find immediately) I don't think that one particular error affects the overall answer, so it's an answer I might consider. However, I think especially in the Harry Potter questions, answers quoting non-canon movie lines as a basis for a canon answer are not unusual.
Is there a guideline on how to handle answers that mix non-corresponding book and movie canon? Or is it just up to the individual user on how to deal with these kind of situations?