[Lawtan]

I'll admit that I find the "just grow up" argument rarely helps the situation get better. In fact, I've only seen it work temporarily on those who are very (Unhealthily) Type A (my father).
You could ask him why he got fired. I don't really have much else of a clue here.

As to the company, perhaps you should try looking up company policy on workloads and such (or for a copy and get Mr. Lazybones to help you look through it). It could help build up a case argument for your higher-ups to have to do more of their work, and if they fire you for that, you could see them in court. (It may depend on the company. If it is a part of chain, they could fear you going to those who license the company out...but if they are big, you'd have little chance of getting anywhere as an individual)
One other thing would be that sometimes hard work does not pay. It can prove you competent, or it could highlight you as a good workhorse for a lazier person who schmoozed their way up to use.

I am not sure if any of this would help, or if it would make things worse. I am not there, so I can't really fix anything. I'm just sorry to see this happen and hope it gets better. *Hugs*