A negative rating is only appropriate if you were either scammed by said person, or you strongly believe that said person is a scammer (see the description of negative ratings on everyone's trust page). I would argue that you should not leave a negative rating against someone unless they meet a fairly broad definition of scammer.
No idea which part you are missing?
1) Betcoin.ag is a publicly
approven scam! If they would provably state the name of the operator, I could sue them instantly for fraud...
2) Promote a publicly approven scam = participation in this scam
3) Participation in a scam = criminal offense
Unless they defraud you, you do not have standing to sue them for fraud.
I don't think that betcoin has been
proven to be a fraud, but would rather say that I strongly believe that betcoin is a fraud (scam).