I also think that cyclists shouldn't ride at speed on the sidewalk, but even if, cyclists causing pedestrian fatalities is extremely rare. It has happened, but it's statistically insignificant when compared to cars killing pedestrians.
There is a big difference between getting hit by 90kg at 30km/h vs 1900kg at 45km/h.
""" From 1996 to 2005, 11 pedestrians across New York City died after being struck by bicyclists.... 2006 to 2013, there were just four pedestrian deaths, according to the city’s Department of Transportation. """ [0]
0: http://www.bloomberg.com/news/articles/2014-09-23/pedestrian...
It is entirely possible that the low bike-on-pedestrian fatality rate is due in part to the law mandating that cyclists and pedestrians be segregated.
Don't get me wrong, all of it counts and is sad and regrettable. I do however think there is an anti-cyclist bias ingrained in the perception and reporting of it's dangers, that's out of whack with the real numbers on accidents.
[1] http://www.thetimes.co.uk/tto/public/cyclesafety/article3758...
But here's the rub - people don't want to put up with even a 1-in-1000 chance of getting a broken arm just from walking on the sidewalk, and they don't want to constantly be on guard against bikes zipping all over the place on what should be a relaxing walk.
It's annoying, and that's why we have things like noise ordnances even though no one ever like, dies because the neighbors are too loud.
I've almost been knocked into a busy 50 mph street by sidewalk cyclists, so yeah.
The real solution is to separate cars and bikes, just like we separate cars and people. Dedicated, buffered bike lanes and safer intersections.