Except that, near as I can tell, CEV is NOT itself in any way based on relativism.
The idea basically amounts to "figure out what criteria people effectively actually mean by 'morality', or more generally, what it is they actually would have wanted if they knew more, spend more time considering moral issues, etc..."
If you believed in objective morality, you would try to figure out what good morals are, rather than take the position (as in CEV) that every moral framework is equally valid from within that moral framework, and therefore you may treat them simply as goals, and all you can do is try to fulfil your goals; and that it makes no sense to wonder about whether you should have different goals/values/morals.
Update: Discussion has moved on to a new thread.
After 61 chapters of Harry Potter and the Methods of Rationality and 5 discussion threads with over 500 comments each, HPMOR discussion has graduated from the main page and moved into the Less Wrong discussion section (which seems like a more appropriate location). You can post all of your insights, speculation, and, well, discussion about Eliezer Yudkowsky's Harry Potter fanfic here.
Previous threads are available under the harry_potter tag on the main page (or: one, two, three, four, five); this and future threads will be found under the discussion section tag (since there is a separate tag system for the discussion section). See also the author page for (almost) all things HPMOR, and AdeleneDawner's Author's Notes archive for one thing that the author page is missing.
As a reminder, it's useful to indicate at the start of your comment which chapter you are commenting on. Time passes but your comment stays the same.
Spoiler Warning: this thread is full of spoilers. With few exceptions, spoilers for MOR and canon are fair game to post, without warning or rot13. More specifically: