Porn vs. erotica seems meant to take us into a realm of conflicting values, disagreements, legalisms, and a large prior literature potentially getting in the way of original thinking - if each of these aspects is meant to be relevant, then can the relevance of each aspect be spelled out?

Well, conflicting values is obviously relevant, and disagreements seem so as well to a less extend (consider the problem of choosing priors for an AI), for starters.