Given that trust is not moderated, and theymos has taken steps to remove himself as "leader" of the trust system, I don't think he would ever come out and say "Users must" or "Users should", so I think "In his view" is the closest we are going to get to guidelines or rules for use of the trust system.

Now, although I don't agree with these ratings, and I wouldn't leave them myself, I'm unlikely to exclude anybody over them. The same is true for feedback left for the other trolls I mentioned in my previous post; in fact, looking at TOAA's trust wall for example, there are more than few users who have left him a negative I don't agree with whom I actively include. No one is ever going to have the exact same standards as you regarding leaving trust, and so your own trust list can never be anything more than a compromise.

As Lauda has pointed out above, there are a myriad of reasons why a user may not want to trade with another user. If you feel a reason warrants negative trust, then I might argue against it, but ultimately you are entirely free to leave said red trust. However, if someone else disagrees with your ratings, then they are entirely free to exclude you so they don't see them. The same unmoderated trust system that permits you to leave ratings others don't agree with, permits others to place exclusions you don't agree with. Exclusions aren't personal attacks, simply a disagreement of opinions, and sometimes a compromise in an imperfect system.