The trust system is not moderated. You are allowed to leave negative trust feedback for any reason (or no reason). If you look at my untrusted feedback, you will notice that I have been trolled for various reasons via my feedback. If you leave someone negative feedback for the sole reason that you do not trust them then others will likely not trust your feedback reports.

EDIT: to clarify my previous statement regarding not trusting you: this is not the main reason why I left my feedback, it does play a minor role but the overriding factor is how you handled the escrow transaction and your initial reaction when it was uncertain that you would be able to recover the account.