There has already been precedent set that simply messaging someone to get them online to set up a meeting (in which a PK could happen) is not against the rules, which is what happened in this case.
Now, onto the metagame accusations - You're only reporting this because you're upset you were PKd, however, this does not mean it won't go unpunished. The problem with your "proof", is that it's circumstantial. It's not enough to directly prove anything. Had you had more proof, serious actions could have been taken. All this does is loop back to my further point of you being okay with the metagame, as it benefitted you. You should have recorded and reported it the second you caught wind of it, but instead you decided to metagame alongside them.
Your appeal has been reviewed and denied.
We have determined this PK to be reasonable and/or justified.
You may not re-appeal this PK.