[ Another long one. Sorry. ]
Sanity has a horizon.
Meaning: Everything you and I do seems sensible to us. Everything other people do seems sensible to them. But not everything you and I do seems sensible to others, and not everything others do seems sensible to you and I.
Everything you and I do seems sensible, of course, because it’s US, and we’re caught up in the subjective immediacy of our lives. We’re inside our own horizon, and everything inside it with us is visible, understandable and comfortable. We naturally find it hard to think of ourselves as wrong or villainous or insane. Everything we do, however weird it might seem to others, seems sane and reasonable to us. Even if we don’t know the reasons, we’re prone to automatically assume SOMEONE knows, and those reasons must be good ones.
On the other hand, other people, out past our own personal horizons of sanity, often do things that seem crazy.