In a sense, insanity can be quite relative. Especially when it comes to groups, what is insane can easily be what makes you different or unusual from others. In fact, whether insanity is good or bad can also be relative. Those who are involved in a particular insane act won't see it as negative, and vice versa.

You've already made a very thorough discussion on insanity in individuals and in groups, but I'd like to open another idea: one that involves insanity and love.

With madness in love, I guess it's still the same idea. When one loves someone, it can be seen or become insanity at some point. But perhaps it doesn't have to have the negative connotation that insanity bears. One can be so madly in love with another that it can actually be quite beautiful.