The time to find out if a piece of plastic can handle a 100 lb bag of water slamming into it is not when that piece of plastic is keeping 100 people alive.

I'm all for restraining any passenger that behaves that way, with or without duct tape.

I'm mostly curious about whether there's a real risk or not of a passenger breaking a window without tools.

If you have a passenger so out of control it tries to break a window, who knows what other actions they will take when their attempt to kill other passengers proves fruitless? Duct tape the hell out of those loons, let the psychiatrist deal with them on landing. Add them to the do-not-fly list while you're at it.

why should it be the design criteria? if people cannot behave, in a safety critical environment - those people shouldn't be allowed in that environment in future. no! the wing design won't change because a 200 lb man wants to jump on it on a whim. that is not its intended function and such failure modes should not be part of this conversation. 'hey lets make entire cockpit out of heavy steel, since we never know some pilot could lose his cool and break some buttons'