Agreed. Cyclists should not be on the sidewalk. Although, I feel that (hopefully) it's the minority of asshole cyclists that would do that.

The same that would run stop signs or red lights, or get on the sidewalk from the road to use the pedestrian crosswalk.

A fast moving cyclist can easily injure a person (especially a child or elderly person) when riding on the sidewalk.

I frequently bike and use the lanes (or street if there are no lanes), just to avoid those possibilities.