I suppose the thing is you have to accept that on a lightweight frame, things get bent quite easily. Had he been riding a DH monster the frame would have shrugged it off, an XC race type bike won't. Lots of tubing is coke can thin anyway so they aren't going to be that resilient.
I'm not an engineer so I won't start wurbling on about technical stuff but as an mtb er who has damaged lots of lightweight frames, but no sturdy ones, this is my experience.
Anyway, as mentioned above.. racing is specifically excluded.
Steel frames on the other hand can be repaired quite easily and IME don't ding/bend/fail quite as easily. That's no help for him though.