Disagree.. Lots of people are killed in secondary colisions. Car A hits car B and car B goes out of control and strikes car C OR a group of pedestrians. One reason that car B goes out is control is the driver is no longer held in place by a seat belt where he/she has a better chance of controlling the car and has been thrown over into the passenger side.
Yes, the othe guy not wearing a seat belt can affect others..
Again this isn't the topic of discussion here. But if you must go that route. I've literally worked hundreds of accidents, and have never once come into that scenario. Thats just a what if scenario. Is it possible? Maybe. But if you hit another car hard enough that you still have inertia to strike a 3rd car and kill the people inside, I doubt your seat belts gonna keep you in control of the vehicle. The extreme shock from hitting the first vehicle will disorient you.
Again I DIGRESS. I'm done with this argument. No more please. Haha!!!!