Comparing a device that essentially allows a Tesla to do what GM does (Hands free active cruise control) today, to a device specifically designed to fire bullets faster to kill more people, is apples to watermelons. Also, one is absolutely illegal under law, the other is not illegal to purchase nor use. So yeah, poor example.No one is arguing the "liability" part of such an event, but the collateral damage, which could very well be another driver or an innocent pedestrian. You don't always hit an inanimate object in an accident.
A better example is guns. Gun owners are always liable for how their guns are used, but why did the ATF ban bump stocks in 2019? Precisely because it's a product that circumvents the legal restriction on owning automatic-firing weapons, just like the counterweight circumvents safety protocols. Sure, most gun violence doesn't involve bump stocks, but that shouldn't prevent outlawing such a device. The collateral damage (or the potential of it) is just too great to ignore its consequences. Similarly, you may be the GREATEST driver who ever owned a counterweight, but that's irrelevant. The device is DESIGNED to circumvent, not to enhance, safety.
As it relates to liability...the driver of a Tesla with or without a counterweight is 100% fully responsible for control of the Tesla whether the car hits a inanimate object or a human. Again, the driver is 100% the responsible party. Same with persons who dont use a weight, but opt to instead, have no hands on the wheel and touch the volume button every 30 seconds (or whatever the current nag interval is)...that driver is always 100% responsible.