Wow that must have been scary, even more considering it wasn't your car. I've had a few close calls, and "hmm why is this happening I haven't done anything to warrant the car getting all out of shape?" Fortunately I got away with it, though I've been knocked off my motorbike and had one big off on my bike in the past.
Good of you to share your experience, it's a sobering thought to all of us, even those of us with dozens of years of experience driving cars, it can happen to anyone.
These things happen, and irrespective of blame or fault, sometimes accidents do happen, even if they were avoidable,and it sounds as though you weren't being over the top in your driving, it sounds as though it's one of those poor conditions, powerful car and not catching it quickly enough, of course not driving within the conditions...
Lastly I don't think anyone should be in be in a position to judge as we've all faltered before, despite not everyone willing to share the experience as eruditely as you have.
At least you're okay and your friend is still talking too you! What did the police say?