Someone suddenly stopping shouldn't be unexpected, nor is it necessarily against the rules of the road. Hacker News is fun and all but consistently gets beaten by 15 seconds of googling e.g. https://www.nytimes.com/2014/05/28/nyregion/double-parking-i...
If you can't see whether there's a large object in your path within time to stop, you're going too fast. There could be a fallen or slow bicyclist in the lane.
You’ve clearly never been going downhill on a bike and had someone illegally stop their car or pull out in front of you. Bikes take more distance to stop than cars.
That’s the point. People in cars have to be able to avoid objects in front of them (whether that’s drivers suddenly stopping or other obstructions) and so do bicyclists.