I have a short stretch on my commute where I ride on the sidewalk because the road is one-way going the wrong way, and the alternative route is about half a mile longer, takes me up a hill, and forces a left turn onto a busy road at an uncontrolled intersection. I have absolutely no problem doing this short distance because (1) it's 6:30 AM and there's nobody else on the road, (2) there are no driveways, and (3) I feel it's actually safer for me. I do go slower because there is one shop, a bar actually, where the owner shows up early and sweeps off the walk in front of his business. He has an iron gate that opens onto the sidewalk and if he did that while I wasn't paying attention and I ran into it, it could be painful.

Doing a short run on a sidewalk is fine as long as you're careful.