Who the hell rides on the sidewalk in a major city? It's faster to ride in traffic in major cities, and since the drivers are usually stuck in heavy traffic, they're less likely to suddenly do something idiotic. It's probably safer for everyone if cyclists ride in the road where they belong downtown, which by itself should be reason enough to ticket lawbreakers. (Of course I'm sure you'll agree that anyone doing 56 in a 55 should be pulled over, too! /s)
That said, if you start ticketing people for riding on sidewalks in the suburbs, pretty soon you won't have any bicyclists at all in the suburbs. Drivers are much, much worse on suburban and rural roads in my experience. Not because they're less skilled or less likely to be texting while slapping the kids and fiddling with the radio, but because they're going faster. Downtown they're all stuck in traffic (haha!).