ludwig, that's because a car in front is a known and avoidable risk: you can see it, so you're supposed to leave a sufficient gap to stop even if he does slam on his brakes.
But where should a cyclist ride to avert the possibility of a pedestrian stepping out in front of him? He did see her, he did sound a horn, and he did swerve to avoid her. Unfortunately for him, she swerved the same way at the last second.
If I could think of anything the cyclist did wrong I'd agree with the judge. But he did everything right. It looks as if the only practical alternative was to have stayed at home.