The problem is this. You are making accusations but you aren't providing any proof, thus how can anyone take your word for your accusations, or why should they? Thulsa Doom said she was in the game and saw what was happening, but still, there isn't any proof showing what happened.
You're telling a squad they need to do something about a member, or you'll contact Zup, but why should they do something when you don't offer anything as proof to your accusations? There was a player named Charles USA, and even though many people complained about his actions, it wasn't until he was caught on video that Zup finally had real good evidence to ban him.
We also had a member in our squad that was denying doing any wrong in a game, and stated "where's the proof". Finally he admitted to actually doing what he was accused of, but he stated that unless someone has proof he will continue to deny he did any wrong. So without any real evidence (aka proof), how is anyone to believe any accusations? Because anyone can claim that any other player did something wrong, correct?
Anyway, now here you are saying someone did something wrong but you're not showing any proof, and that is the issue.
As I said before, first contact the officers of the squad, and give them the proof of what happened. If this player is a constant problem (and from what Thulsa Doom says, he is), the you can post in the blacklist thread, but also post the proof of what he/she is doing, rather than just creating a slam thread with no evidence.