I don't think it's bad to think the best of people. Everyone has light and darkness in their heart - and I like to think people listen to the light more than the dark. It's what keeps the worlds bright, after all.
It's just sad, when people lose their light.
[He says all this with perfect seriousness and a real sort of sadness at the thought of it, and if he saw the warning signs of a worsening mood, he chose to ignore them. Probably he just didn't in the first place.]