If you were walking down the road carrying a running chainsaw, and someone ran round the corner into you and got their arm lopped off, it would be their fault for running into your path unexpectedly, but it would also be your fault for operating potentially dangerous machinery in a public place.
If you were driving down the road and someone ran round the corner into you and got their arm broken, it would be their fault for running into your path unexpectedly and I doubt that an English court would hold you part-responsible for operating potentially dangerous machinery in a public place. But German law, apparently, would.
The only real difference between the two scenarios is that we expect to see cars on the roads and we don't expect to see chainsaws, but is that actually a good enough reason that anyone who gets tangled up in one "deserved what he got", or should we expect drivers to operate with more care anyway? Or does it depend on the setting? Hitting a child who steps out behind an ice cream van on a residential road is already regarded quite differently from if they run across a motorway