The facts are a bit confused to judge. The issue is whether Goldman knew the bonds were hand picked by a third party as likely to underperform vis a vis similar grade bonds that were put into the pool, and failed to disclose such methodology, if in fact that occurred. If it was more of just a generic bet against low grade bonds, then I don't think anyone would care much and the non disclosure would thus not be material.
I believe in a sense, it should be OK to write a bad derivative and bet against it, as long as there's full information of course.
