If they're on meds, and still like that, then just... tolerate them.
Some people have it milder than others, but from what it sounds like, your friend is suffering pretty badly. Meds generally regulate people fairly well, but it doesn't sound like it's helping here. If that's the case, the best you could suggest is that they look into other medications. Besides that, try to offer some sympathy. Don't treat it as merely bad behavior. It's an illness like any other.
I get this...but, I'm not asking how to "judge" him, I know it's an illness. I'm asking, how to "deal" with them, how to treat them. Obviously I am tolerating him, but it's not really helping anyone, I am trying to do something worthwhile with my time, so is he, and there are people who need my time more.
The point I am making is, I don't know how this illness works, but I'm not going to spend my time babysitting some guy who I owe nothing to, who has had much more privelige in his life than me, is the same age as me, etc.
Also I can't "cut links" really, as we're running a "project" together, we're the only two in a small town some distance from the rest of the organization, etc. But I can't be bothered getting bogged down ins pecifics, I am asking for general guidelines on the condition from people with experience.
But the question is, how do I go about "not babysitting" though? Be honest and strive to help him through telling it like it is, while encouraging good signs? Make excuses? Cut links? "Firm but fair". And how much "firmness" can someone with this condition handle?