Zen888!!! The answer to this is a resounding YES!!! (And I'm sure you already know it though. Still, let's say it again. YES!!!)

Unfortunately, your experience can be pretty common, wherein people start to attribute everything to the disorder and/or define the person by the disorder. We're still regular people (imagine that! ), we just have a lot more and more intense rough patches where things can get out of hand for us. But it's not usually a constant state of affairs (though it can certainly seem that way sometimes!) And even *if* we're in a mood state, doesn't mean that _every_ comment, reaction etc is caused by it. We are allowed to be angry if someone causes us justifiable anger. When something sad happens, we can be sad. Doesn't mean we're depressed (and as we all know, they're very different anyway, though someone who's not been seriously depressed will not be likely to really understand this.) We can laugh a lot at a funny movie -- doesn't make us hypo/manic!
Even with the lack of insight factor, if we are paying attention, we can often pick up on warning signs... patterns or behaviors that when they escalate have gotten us into trouble before. And when that happens, you could inform him to keep an eye out if you feel he could be geniunely helpful in such a circumstance.

Have you had the dx for long? Do you think that he could learn more and come to understand that he is overreacting? Sometimes it could be a matter of adjustment and learning, but if this has been going on a long time and/or he's not willing to change it, well that's not very helpful or supportive for you. Most books I've seen warn against this very thing for those wanting to be helpful. Has he read any? Would he be willing to? I just wonder if he would "get it" better if it's coming from a book or doc or whatever --something outside?

Wishing you good luck with this and keep us posted!