The most subjective part of the rating is, of course, "content". And while people are free to judge and rate the content by whatever criteria they choose, my only complaint is when people give low ratings because they simply dislike the genre.
In this case we are asked to be reviewers/music critics and as such, ideally we would judge the content within its musical context. To give an album a "1" for content because it's heavy metal and I can't stand heavy metal makes the review meaningless. It might be considered the greatest heavy metal of all time by fans of the genre, but my giving a "1" anyway only exemplifies MY ignorance, rather than any actual weakness in the content.