Lol, I wonder if the Glock pistols were feared this much when they first came out.
the only part I wouldnt trust being polymer would be the upper. Everything else (like the stock and the grip, handgaruds, lower, LPK, etc can be as plastic as it wants. Its not a pressure containing component, and plastic can flex a heck of a lot better than aluminum.
Anyone who owns an M9 or PA-63 knows that aluminum is NOT good at flexing, and will eventually wear out and crack (M9 lifespan is what... 5000 rounds until the frame cracks?)