This isn't the reaction that Rodimus was expecting at all, although it makes more sense than the intense and uncharacteristic anger brewing just a moment before. Optimus seems to shut down, and Rodimus feels his spark drop like a cold weight.

"Optimus...I...." Damn it. He puts his head in his hands; this isn't what he'd meant to happen. He'd gotten reactionary, gotten defensive and now...well, he's never seen Optimus like this before. He feels sick with guilt, and even that makes him feel guilty because it's ultimately a self-serving emotion. He wishes desperately that he could be somewhere else.