Disaffected ex-employees are about as new and innovative as composite material airframes. If this individual truly has an axe to grind, he might well have reconsidered the timing of his "bombshell", saving it as he did until he himself has been accused of gross professional misconduct.
Not only are these materials being used extensively on aircraft today, but the techniques and methods required for testing and certifying are well understood. To give credence to his theory is to accept that both the FAA and Boeing are colluding in some mass conspiracy to short circuit the certification process for commercial aircraft. The FAA can certainly do incompetence, but they struggle mightily with conspiracy. As for Boeing's motive to expose the travelling masses to such an unquantifiable risk, has anyone noticed the propensity with which Americans sue each other? It's almost a given that composite materials will behave differently to traditional metals, they will produce different toxins under combustion, but does that greatly change the survivability index in a crash over a traditional structure? Only the certification process will establish that, not some shotgun blast of accusations and generic blame throwing.
Incidently, linking it with the Shuttle experience simply demonstrates that e-mail is the preferred media for communicating dissatisfaction within a large anonymous organization, but provides little additional insight.