The 3/10 was obviously meant to make a statement (towards Capcom that they're taking the wrong path with the Resident Evil series) and not to reflect the actual quality of Resident Evil 6. So no, it's not justifiable even if you happen to use the "art" approach of judging video games.
Now, as much as i hate the modern Resident Evils I still don't think it's cool to make a statement through your review score. Review scores should be comparable to each other.