You really understand Riku well. There are a lot of people who write stuff like this, but you nailed it. Truly, if you think about it, this is exactly Riku's opinion on the matter, nice job.
Riku admitting his weakness and his strength - Darkness and his friends. I feel that he's the sort of person who sit down to think about it rationally and not beat himself up too hard over it. He understands why he does it and admits to it.
Sora and Kairi are forgiving and kind. They'd never leave Riku, even after all the things he'd done because they still believe in him and he's their friend.