It would depend on just how bad the ding/dent was, for me. Something huge and instantly noticeable (e.g. were the same level of damage to happen to my car, I'd get it repaired), then, no, I would want a new box).
If it were something that was more easily concealable, I'd accept a hefty discount/free tools, and still be pretty darned happy about it.
Either way, there'd be no way that I'd just accept the box as-is, and the implied suggestion that you **** it up (because you're buying build-quality, not appearance) is just utterly ridiculous.
They sold you an undamaged box. Had the freight company or whoever not screwed up, you would have gotten an undamaged box. Why, then, should you accept a damaged box without compensation?
You're really in the driver's seat here - I mean, I'm not suggesting that you try to negotiate for a free box, but ultimately, you either accept the damaged box with whatever discount and free stuff you deem appropriate, or you get a new box. Those are the only options the dealer/company should have.