Not baseless, data-driven. This isn’t, like, my opinion, and this is the reason it’s illegal for adults to ride on sidewalks in many municipalities.
There are more obstacles on the sidewalk, and sidewalk is more prone to be uneven. Most bicycle accidents aren’t bike vs. car, but now vs. environment: unexpected bumps or drops, debris, obstacles like poles and tree branches.
But the real problem is visibility. People step out onto sidewalks not expecting a speeding cyclist, risking collisions. But more importantly for your safety, motorists aren’t expecting you there, either. So when you are going across intersections, they cannot see you –because you’re in the wrong place, and because as you point out, there are streetlights and sign poles and other objects between you– and may turn into you .