It's easy to find information that will tell site users that questions that attract opinion-based answers are bad ("good subjective bad subjective", the tour ("Avoid questions that are primarily opinion-based, or that are likely to generate discussion rather than answers."), "where do we draw the line on opinion based questions", etc.
It seems like an obvious corollary to me that answers should be objective and provide supporting evidence, but (getting meta-meta for a minute here) I don't see anywhere I can point to for a reference to back up that opinion. The tour says you should answer well-asked questions, should provide context for links, etc., but nowhere does it say explicitly that you should back up your answer with concrete evidence, or what kinds of evidence are allowed/preferred.
The closest I can find is this, from "Good Subjective, Bad Subjective":
Back It Up! means that your answers must be based on either:  Something that happened to you personally  Something you can back up with a reference
which seems reasonable, but is in the middle of a long post about opinion-based questions (and refers to a FAQ from another site, although the implication is that this principle applies broadly across SE); I was looking for some kind of brief restatement of this principle in the user documentation for SFF (e.g., Skeptics.SE has a detailed description of their referencing policy in a meta FAQ).
Someone has posted (IMO) a subjective answer about the significance of a scene in the LoTR movies and is arguing in the comments that they don't know what kind of references are required/should be required to support a statement, saying "Literary interpretation is inherently opinion, not factual". (The other answer to the question provides quotations from Peter Jackson, so the question is not intrinsically "opinion-based".)
your answer looks like a fact ("it represents blood as Peter Jackson couldn't make the battle as bloody as he wanted because of censorship") and as such it has to/should be backed by something other than "I think so"
and I agree with them, but I'm wondering whether there is anywhere in the site documentation that actually states this guideline ... ? If not, then I guess this is a feature request (maybe a section under How to Answer ? ...