Cars regularly mount pavements/sidewalks as well, and kill pedestrians who are not even in the road.
The correct response to "cars make cities unsafe for everyone" is of course to ban all but the most essential cars from cities. It is not to suggest that the _other_ forms of transport (including walking on the pavement/sidewalk!) are so unsafe as to be irresponsible, in the presence of cars.
And also "cars bad" too. Lots of people making left turns across the bike lanes without checking their mirrors (probably happens once per thirty minute ride), people executing half a left turn and then blocking the bike lane to wait for pedestrians, people parking in the bike lane. It's been 20 years since I had a car wreck so I can be reasonably sure when I put my kid in their car seat that it will be an uneventful trip. City biking is always at least a little eventful and there's a lot less protection though. If society has given me a nice lane to ride the bike, is it still society's failing that my fellow occupants of the lane act the way they do?
But it isn't. End of story.
Happy to support people who want to make biking safer. Happy to support politicians who want to build protected bike lanes.
But you can't just make up a fairy tale land and pretend it's safe. Bring yourself back to real life, and your children are in danger.
In my city, it's not if but when you'll get hit by a car on a bike. Yet I see parents increasingly think it's okay to haul their children on their bikes.