I didn't even think this thing was that fragile. Seriously, I just drove on the highway, a small rock flew out from under the wheels of an oncoming car, and then I saw a dent. Is that normal? Or is my bumper defective?
Yeah, I think it's normal. I mean, the rock flew out with force, and your bumper clearly isn't armored to handle that. Lucky it didn't hit the windshield, that's actually a super common cause of cracks.
If you have a basic bumper, like the stock one, yeah, they're often too flimsy and soft. It's no news that any little rock flying from the wheels of the car in front and bam, you have a dent. I suggest checking out aftermarket bumpers https://bumperstock.com/collections/2003-2006-chevy-silverado-2500-3500 (https://bumperstock.com/collections/2003-2006-chevy-silverado-2500-3500), especially if you often drive outside the city, off-road, and in situations where it's better to think about car protection.