So John,

Wouldn't your own argument apply equally if not with greater meaning to bicyclist against motor vehicles?

Is it not far more likely that a 4000lb mass traveling at 60 mph will do more damage to a 200lb mass moving at even 40mph ?

I'm thinking you're envisioning bicyclists traveling on sidewalks at 40+ mph and I don't think sidewalks are very accommodating for high speed travel in the first place.

On the sidewalks, it's usually difficult to have space to reach speeds that great.

As I ride about, I see the VAST MAJORITY of bicyclists ON the sidewalk. NOT on the road. It's just insanely dangerous.

But again, I do believe that varies from location to location.

I have never, nor do I know anyone who has ever collided with a pedestrian on a sidewalk. 12mph is just not that fast. Plenty of margin for safety.

Perhaps your logic applies best to someone lacking courtesy skills and or respect for others? If you are doing 12mph and see pedestrians ahead, slow to 4 mph while passing. Anticipate their moves or alert them to your approach. But certainly do not rush with reckless abandon and disregard for their safety just because you are on a bicycle. Mutual respect...I think that's key.

I did see a group of young kids in a Mustang GT recently swerve toward a bicyclist on a bike path and apparently they felt it was humorous.
There are too many like that behind the wheel. It is dangerous enough when you are on the road protected by steel surrounding you...

If you really believe that painted line offers protection....wow.