Why does Peter Sullivan do anything or report the firm's risky position?

According to this article:

Imagine if Merrill Lynch had been smarter, like Goldman Sachs, a few years ago. The investment bank would have realized it was holding too many dodgy mortgage securities and sold them off to buyers who didn’t yet think the market would blow. Those clients might have then landed in trouble. But Merrill would have avoided a fire sale to Bank of America.

That’s the basic premise behind the latest film to emerge in the financial crisis genre, “Margin Call.”

[...]

Of course, all this sounds a bit like the story of Merrill Lynch. The firm found itself with tens of billions of dollars of similarly dodgy mortgage securities it couldn’t sell and whose losses threatened to overwhelm its capital. As Lehman Brothers was going under, Merrill had to sell itself to BofA in a hurry three years ago in September.

But “Margin Call” posits a different end for its fictional firm. Over the course of a few hours, Chief Executive Tuld, whose name rather obviously rhymes with that of Lehman’s disgraced ex-boss, convinces his troops that they must sell every lick of MBS on the balance sheet, knowing full well that the assets are essentially worthless.

So the movie promotes a kind of "what if" scenario. But why?

In reality, dumping massive amounts of mortgage bonds in a heartbeat before everyone else had worked out they were toxic would have been nearly impossible. But the fictional dilemma is one worth considering – at least for the director it was. His father was a senior executive at Merrill.

As for Peter's motive: if he helps save the firm, there's a good possibility he gets to keep his job (or even a promotion). Plus: if it happened at this firm, there is a good chance it also happened at other firms, so sending out resumes in the hopes of scoring a new job at a time when the market is flooded and there are fewer job opportunities isn't exactly a wise strategy.

But IMHO this is a movie that isn't about the people involved in the story, this is a movie about the systems (and their failures), and a fantasy as well. Looking for motivations and character arcs etc. is pointless, that isn't what this movie is about.

Note that (this is a quote from Wikipedia):

the plot has similarities to some events during the 2008 financial crisis: Goldman Sachs similarly moved early to hedge and reduce its position in mortgage-backed securities, at the urging of two employees, which essentially mirrors Tuld's comment about the advantage of moving first.