Sora just felt...offended. Corin didn't know anything about them, about their relationship. He just assumed that they behaved like Master and Servant, even ones that were in love. Sora may be Prince, but even from the beginning they had never behaved as a traditional Master and Servant. Besides, what made Corin think that Riku was better off back with his family, strangers in a home he barely knew with no skills to support himself, than life in a castle with the boy he loved?
"Riku is able to think, speak, and decide things for himself, within the law of our country," the Prince replied. "I have never forced, persuaded, or pushed him into anything." Gently nudged maybe. Made his intentions and feelings known. "He does not stay with me simply because I want him to. He does not do things that I want him to simply because it makes me 'happy'. To suggest this is...well it is offensive to me and to Riku."
The Prince didn't want to talk about it anymore. "I do not see why my solutions are inadequate. If you desire something different, perhaps ask him about it. He is an adult, and is more intelligent than I think you give him credit for." The Prince did all he could given the circumstances. "I will not attempt to sway his decision either direction," he promised. He never had! And if just existing as Riku's love was swaying, well too bad. He sure as hell wasn't going to try and tell him to leave. Corin didn't understand how Sora needed Riku, and Sora thought this was better for Riku anyway.