The feedback left by SiNeReiNZzz is an abuse of the trust system in my opinion, trust feedbacks are not a way to get back at other members whether or not you were wrongfully accused.
He clearly deserves to be out of the DT circle and a red trust for his plagiarism.
Red trusts is not the penalty for forum offences, such offences are moderated and should be handled by the mods, in extreme cases where a user poses an immediate threat to the community (like when an account is hacked) red trust can be used to warn other members, I however do not think it should be used in cases like this.
Did you report the post in question to the mods? This usually draws their attention faster than posting in the report thread, you should note that cases are handled individually and other factors go into the final decision with mods allowed to use their personal discretion when handling cases.