Oh come on. This argument doesn't articulate any reasonable way to limit this principle. If someone rams my car from behind, do they get to say "this is you're fault; if only you hadn't been out here driving, I wouldn't have hit you."

As I've said above, the courts have given up using this rule, because there's no reasonable way to limit it. Fault is relative now, in almost all courts. Each party is liable to the extent of their own contribution to what transpired.