This protective UV filter did its job, protecting a $2,000 lens from an impact strong enough to dent its aluminum frame. The filter was so jarred by the damage that we could remove it only after tapping with a chisel to loosen the threads then twisting with a rubber strap wrench.
Keeping fragile and expensive equipment from harm is often not always about avoiding all peril. That would require just leaving your cameras and lenses at home. More often, you protect your gear by surrounding it with sacrificial items; plastic caps, glass protectors and cases both soft and hard. While you would prefer to never have a scratch appear on any of your stuff, it's better when it's a rip to the camera bag instead of a gash across the LCD screen or a dented UV filter instead of a cracked lens body.
Had the plastic hood been in place when this filter received the blow, a broken hood may have been the only damage.
Lens Lenders includes a glass protector with nearly all of our lenses. (They're impossible on fisheye lenses and telephotos with giant front elements.) We also recommend using lens hoods at all times, indoors and out. While the primary purpose of a hood is to reduce flare, they have additional value as a "crumple zone" when your tripod tips over or the lens slips from your hands.