Wow Bird Feeder, I'm so sorry, what an awful situation with your insensitive boss! That's terrible.

He shouldn't be able to find out what kind of treatment you're receiving, and he absolutely shouldn't be allowed to fire you for it, but I hear you on how hard that can be to prove...

The things he's saying would make me very, very uncomfortable. How is your HR department? How big is the company? Do you think you'd feel comfortable talking to someone from HR, and mentioning that he's making statements that could really make things uncomfortable for people suffering from a medical condition (depression, or anything, it sounds like?) He's acting badly for the company, I think, and possibly putting them in danger (since if somebody sued, I assume they'd sue the whole company).

A really good site that sometimes talks about this is Ask a Manager - the woman who blogs there is really smart, and not afraid to talk to experts (lawyers, for example) for more info when she's not sure about something. This sounds like something she may have addressed (or something similar), so you may want to check that out and see if there's anything relevant.

Again, I'm so sorry. It's hard enough to deal with depression, you shouldn't have to deal with your boss being an idiot on top of that!