[Twosugars]

I don't know what people think bipolar is, but it is not insanity. Stephen Fry is bipolar, for example.
Afaik, it is depression interspersed with periods of mania, i.e hyperactivity, grand plans etc. (like a opposite of depression),so mood swings both ways.
Of course, bipolar people can suffer from other, co-morbid mental conditions which may or may not include psychosis which is what we commonly think of as insanity, i.e. lack of touch with reality (delusions, voices etc), for example schizophrenia etc
But just bipolar doesn't make you cruel or crazy. Unbalanced - yes: sometimes depressed, sometimes over the top.
Plus bipolar comes in two types, 1 and 2, mild and severe.