My point was that the car's mass at the point of impact doesn't matter, because the cyclist doesn't die of an immediate trauma from the collision. He could be tipped over by a pedestrian, or bad street conditions.

He dies – as you put correctly – because of all the cars around him. Of course kinetic energy is relevant there, but it doesn't matter to the argument, because the claim was that being touched by a car is much more dangerous than being touched by a cyclist. And that's wrong.

As soon as the cyclist falls he's in mortal danger.