If anything, the Second Knossos raid would be excellent Terra propaganda. Consider:
It was an operation conducted with no support, and with the most advanced weapons available to the Terran arm of the GTVA.
It was one of the only operations in the war with confirmed ZERO causalities.
It provided key intelligence about the scope of the Shivan invasion, and likely was used to justify the nuking of both subspace nodes.
It inflicted, relatively speaking, spectacular causalities on the Shivans. In that mission you could achieve, if you did it perfectly, the sinking of the three Shivan cruisers, around fifty fighters and bombers, and three previously unseen Shivan communication nodes.
Take for example the raid on Osama Bin Laden, while parts of that operation are still classified, it's positive affect on morale was too extreme to leave it completely classified.