It's astonishing how bicycle riders seem to think everybody except for them is responsible for their safety.
Riding on the sidewalk is outright dangerous, I have seen multiple accidents when:
* pedestrians got hurt by bicyclists travelling at high speed riding on the sidewalk
* bicyclists go around corners and hit pedestrians
* bicyclists get hit by cars who couldn't see them at the intersection because they were riding on the sidewalk
If a cyclist and a pedestrian collide, someone might go to the hospital. If a cyclist and a car collide, someone is likely to die, and it's basically always the cyclist.
In reality, though, we all have to get along. And those concerns are addressed by cyclists not riding at breakneck speed and going blindly around corners. I don't see either of those behaviors very often in my area.
I'm amazed at how often a bicycle rider on the sidewalk will actually warn me to get out of the way. I haven't knocked anybody off of one yet. It's only a matter of time before somebody bumps into me on one and gets hurt.