[Mowdit]

Am buying a dash cam !
Not as a deterrent, but can you imaging your insurance company saying "not paying, you caused/provoked this !
Cam would be cheap insurance and prove to the police whom the culprits are.

I'd drive to the nearest police station, with my hazards on whilst flashing my high beams constantly (you never know when a blue and white is driving past)

Hope your mate recovers, the XR is fixed back to new (ish) and a lesson is learnt