Putting it another way, if and only if we exercise due care and caution with special attention to strictly limiting our speed, riding on a sidewalk or a MUP in the usual sidewalk position can be a safe alternative to an otherwise unsafe route.

Speed control is, I think, a problem. Almost all my riding is on streets and roads but few years ago I regularly rode a few hundred feet of sidewalk to avoid a really bad alternative and had to work hard at convincing myself to move slowly enough to make that choice the safe one.