This was indeed a tragic accident, as are all collisions that result in death or serious injury.
My question to the OP is, are you also campaigning against other car manufacturers that use third row seats? I know that Mercedes still offers station wagons with 3rd row rear-facing seats, and I know that Volvo did for a long time. Both Mercedes and Volvo are well-known for safety consciousness -- how does the Tesla design compare to those? There may be other manufacturers as well, especially for vehicles not sold in the US. For that matter, what about 3rd row forward-facing seats in various other types of cars, wagons, crossovers, SUVs -- are they all viewed as somewhat more hazardous than other seat positions? Should they be prohibited? And if we are to have that discussion, I would suggest that we need some facts that seem to be missing from this discussion so far, namely what are the actual statistics on deaths and injuries in various seating positions. E.g., it could be that 3rd row seats are safer in certain types of collisions (further from the point of impact in a head-on collision) or that the safety of seats depends more on distance from the front or rear, or body design, or any of a number of factors, than on row position itself.
So I very much appreciate the OP's concern for the safety of his children and others, and there may indeed be a valid point to be made about the relative safety of various seating positions, but I think a data-based discussion would be more useful than to speculate and argue without hard facts. I wonder if the IIHS or NHTSA has any stats on this type of thing that would be publicly available?