That quote about vicarious liability contains a lot of misinformation. For one thing, in nearly all states, parents are not liable for the torts of their children, except (by statute) for some cases of malicious property damage, and those statutes often include low limits on liability. Car owners' liability for the negligence of others driving their cars is imposed by statute in many states under "owner liability laws"; it has nothing to do with the driver being considered the owner's "agent." This has nothing to do with contributory negligence, which refers to negligence on the part of the plaintiff, not the defendant, and which has been replaced in most states by comparative negligence. If people don't follow or enforce safety rules and someone is hurt as a result, liability isn't "vicarious," it's just ordinary liability for negligence.

There are, to be sure, lots of cases going pretty far to hold people liable (think McDonald's hot coffee). That's why we have liability insurance, and it's the main reason AMA membership costs as much as it does.