friends dictating terms on friendship

If this person really is bi-polar, then you've got to figure out whether or not you can/shoul deal with them at all. Sometimes it's best to cut your loses and lose contact with the person, but you'll figure out what's best in your case.

I strongly believe that you should tell a friend when they do something wrong. And in most cases it should be done in a constructive way, if they are receptive to such things (Some people won't take you seriously unless you are 'mean' about it). What else is a friend for, if not to tell you things as they are? What's the old saying? A friend is someone who will tell you your breath smells?

There is a world of difference between telling someone where they have done/said something wrong, and insulting someone. If your friend feels the need to judge people, and tell them off for the sake of it, then that's wrong. A lack of tact is something that anyone can change. Unfortunately a lot of people who act poorly like that expect others to 'just deal with it' instead of attempting to improve on their personal skills. His 'hating himself' due to his treating others poorly is a thinly veiled attempt to garner sympathy and have others overlook his attitude problems.

Jam it back in, in the dark.