[Zatyme]

I don't think he's ashamed of being an Orphnoch (what with him objecting taking offense that they need to be made "human" again to be accepted) and more afraid of that darkness in him that he might associate with his Orphnoch side what with both coming to light at the same time in the narrative and that's what he's trying to repress and deny due to it running counter to his true nature. That no matter what he does or says that dark side of him is the correct choice and the sole truth of living as an Orphnoch, that he has to give up his compassion in order to survive. The fact that all of his fears are being played on by this betrayal by Humanity as a whole is tearing him apart and without knowing the truth of Yuka's story in this episode that the guy she likes now is Keitaro the only guy nicer than him.